Chapter Questions
Which of the following is a correct unit of energy?a) $\mathrm{kg} \mathrm{m} / \mathrm{s}^{2}$c) $\mathrm{kg} \mathrm{m}^{2} / \mathrm{s}^{2}$e) $\mathrm{kg}^{2} \mathrm{~m}^{2} / \mathrm{s}^{2}$b) $\mathrm{kg} \mathrm{m}^{2} / \mathrm{s}$d) $\mathrm{kg}^{2} \mathrm{~m} / \mathrm{s}^{2}$
An $800-\mathrm{N}$ box is pushed up an inclined plane that is $4.0 \mathrm{~m}$ long. It requires $3200 \mathrm{~J}$ of work to get the box to the top of the plane, which is $2.0 \mathrm{~m}$ above the base. What is the magnitude of the average friction force on the box? (Assume the box starts at rest and ends at rest.)a) zerob) not zero but less than $400 \mathrm{~N}$c) greater than $400 \mathrm{~N}$d) $400 \mathrm{~N}$e) $800 \mathrm{~N}$
An engine pumps water continuously through a hose. If the speed with which the water passes through the hose nozzle is $v$ and if $k$ is the mass per unit length of the water jet as it leaves the nozzle, what is the power being imparted to the water?a) $\frac{1}{2} k v^{3}$b) $\frac{1}{2} k v^{2}$c) $\frac{1}{2} k v$d) $\frac{1}{2} v^{2} / k$e) $\frac{1}{2} v^{3} / k$
A $1500-\mathrm{kg}$ car accelerates from 0 to $25 \mathrm{~m} / \mathrm{s}$ in $7.0 \mathrm{~s}$. What is the average power delivered by the engine $(1 \mathrm{hp}=746 \mathrm{~W}) ?$a) $60 \mathrm{hp}$b) $70 \mathrm{hp}$c) $80 \mathrm{hp}$d) $90 \mathrm{hp}$e) $180 \mathrm{hp}$
Which of the following is a correct unit of power?a) $\mathrm{kg} \mathrm{m} / \mathrm{s}^{2}$b) $\mathrm{N}$c) Jd) $\mathrm{m} / \mathrm{s}^{2}$e) W
How much work is done when a 75.0 -kg person climbs a flight of stairs $10.0 \mathrm{~m}$ high at constant speed?a) $7.36 \cdot 10^{5} \mathrm{~J}$b) 750 Jc) 75 Jd) $7500 \mathrm{~J}$e) 7360 J
How much work do movers do (horizontally) in pushing a $150-\mathrm{kg}$ crate $12.3 \mathrm{~m}$ across a floor at constant speed if the coefficient of friction is $0.70 ?$a) 1300 Jb) 1845 Jc) $1.3 \cdot 10^{4}$.d) $1.8 \cdot 10^{4}$ Je) $130 \mathrm{~J}$
Eight books, each $4.6 \mathrm{~cm}$ thick and of mass $1.8 \mathrm{~kg}$, lie on a flat table. How much work is required to stack them on top of one another?a) 141 Jb) $23 \mathrm{~J}$c) $230 \mathrm{~J}$d) $0.81 \mathrm{~J}$e) 14 J
A particle moves parallel to the $x$ -axis. The net force on the particle increases with $x$ according to the formula $F_{x}=(120 \mathrm{~N} / \mathrm{m}) x$, where the force is in newtons when $x$ is in meters. How much work does this force do on the particle as it moves from $x=0$ to $x=0.50 \mathrm{~m} ?$a) 7.5 Jb) $15 \mathrm{~J}$c) $30 \mathrm{~J}$d) 60 Ie) $120 \mathrm{~J}$
A skydiver is subject to two forces: gravity and air resistance. Falling vertically, she reaches a constant terminal speed at some time after jumping from a plane. Since she is moving at a constant velocity from that time until her chute opens, we conclude from the work-kinetic energy theorem that, over that time interval,a) the work done by gravity is zero.b) the work done by air resistance is zero.c) the work done by gravity equals the negative of the work done by air resistance.d) the work done by gravity equals the work done by air resistance.e) her kinetic energy increases.
Jack is holding a box that has a mass of $m \mathrm{~kg} .$ He walks a distance of $d \mathrm{~m}$ at a constant speed of $v \mathrm{~m} / \mathrm{s}$. How much work, in joules, has Jack done on the box?a) $m g d$b) $-m g d$c) $\frac{1}{2} m v^{2}$d) $-\frac{1}{2} m v^{2}$e) zero
If negative work is being done by an object, which one of the following statements is true?a) An object is moving in the negative $x$ -direction.b) An object has negative kinetic energy.c) Energy is being transferred from an object.d) Energy is being transferred to an object.
The work-kinetic energy theorem is equivalent to a) Newton's First Law.b) Newton's Second Law.c) Newton's Third Law.d) Newton's Fourth Law.e) none of Newton's laws.
Kathleen climbs a flight of stairs. What can we say about the work done by gravity on her?a) Gravity does negative work on her.b) Gravity does positive work on her.c) Gravity does no work on her.d) We can't tell what work gravity does on her.
If the net work done on a particle is zero, what can be said about the particle's speed?
Paul and Kathleen start from rest at the same time at height $h$ at the top of two differently configured water slides. The slides are nearly frictionless.a) Which slider arrives first at the bottom?b) Which slider is traveling faster at the bottom? What physical principle did you use to answer this?
Does the Earth do any work on the Moon as the Moon moves in its orbit?
A car, of mass $m$, traveling at a speed $v_{1}$ can brake to a stop within a distance $d$. If the car speeds up by a factor of $2,$ so that $v_{2}=2 v_{1},$ by what factor is its stopping distance increased, assuming that the braking force $F$ is approximately independent of the car's speed?
The damage done by a projectile on impact is correlated with its kinetic energy. Calculate and compare the kinetic energies of these three projectiles:a) a $10.0-\mathrm{kg}$ stone at $30.0 \mathrm{~m} / \mathrm{s}$b) a 100.0 -g baseball at $60.0 \mathrm{~m} / \mathrm{s}$c) a $20.0-\mathrm{g}$ bullet at $300 . \mathrm{m} / \mathrm{s}$
A limo is moving at a speed of $100 . \mathrm{km} / \mathrm{h}$. If the mass of the limo, including passengers, is $1900 . \mathrm{kg}$, what is its kinetic energy?
Two railroad cars, each of mass 7000 . kg and traveling at $90.0 \mathrm{~km} / \mathrm{h}$ collide head on and come to rest. How much mechanical energy is lost in this collision?
Think about the answers to these questions next time you are driving a car:a) What is the kinetic energy of a $1500 .-\mathrm{kg}$ car moving at $15.0 \mathrm{~m} / \mathrm{s} ?$b) If the car changed its speed to $30.0 \mathrm{~m} / \mathrm{s}$, how would the value of its kinetic energy change?
A $200 .-\mathrm{kg}$ moving tiger has a kinetic energy of $14,400 \mathrm{~J}$. What is the speed of the tiger?
Two cars are moving. The first car has twice the mass of the second car but only half as much kinetic energy. When both cars increase their speed by $5.00 \mathrm{~m} / \mathrm{s}$, they then have the same kinetic energy. Calculate the original speeds of the two cars.
What is the kinetic energy of an ideal projectile of mass $20.1 \mathrm{~kg}$ at the apex (highest point) of its trajectory, if it was launched with an initial speed of $27.3 \mathrm{~m} / \mathrm{s}$ and at an initial angle of $46.9^{\circ}$ with respect to the horizontal?
A force of $5.00 \mathrm{~N}$ acts over a distance of $12.0 \mathrm{~m}$ in the direction of the force. Find the work done
Two baseballs are thrown off the top of a building that is $7.25 \mathrm{~m}$ high. Both are thrown with initial speed of $63.5 \mathrm{mph}$. Ball 1 is thrown horizontally, and ball 2 is thrown straight down. What is the difference in the speeds of the two balls when they touch the ground? (Neglect air resistance.)
A $95.0-\mathrm{kg}$ refrigerator rests on the floor. How much work is required to move it at constant speed for $4.00 \mathrm{~m}$ along the floor against a friction force of $180 .$ N?
A hammerhead of mass $m=2.00 \mathrm{~kg}$ is allowed to fall onto a nail from a height $h=0.400 \mathrm{~m} .$ Calculate the maximum amount of work it could do on the nail
You push your couch a distance of $4.00 \mathrm{~m}$ across the living room floor with a horizontal force of $200.0 \mathrm{~N}$. The force of friction is $150.0 \mathrm{~N}$. What is the work done by you, by the friction force, by gravity, and by the net force?
Suppose you pull a sled with a rope that makes an angle of $30.0^{\circ}$ to the horizontal. How much work do you do if you pull with $25.0 \mathrm{~N}$ of force and the sled moves $25.0 \mathrm{~m} ?$
A father pulls his son, whose mass is $25.0 \mathrm{~kg}$ and who is sitting on a swing with ropes of length $3.00 \mathrm{~m}$, backward until the ropes make an angle of $33.6^{\circ}$ with respect to the vertical. He then releases his son from rest. What is the speed of the son at the bottom of the swinging motion?
A constant force, $\vec{F}=(4.79,-3.79,2.09) \mathrm{N},$ acts on an object of mass $18.0 \mathrm{~kg},$ causing a displacement of that object by $\vec{r}=(4.25,3.69,-2.45) \mathrm{m} .$ What is the total work done by this force?
A mother pulls her daughter, whose mass is $20.0 \mathrm{~kg}$ and who is sitting on a swing with ropes of length $3.50 \mathrm{~m}$, backward until the ropes make an angle of $35.0^{\circ}$ with respect to the vertical. She then releases her daughter from rest. What is the speed of the daughter when the ropes make an angle of $15.0^{\circ}$ with respect to the vertical?
A ski jumper glides down a $30.0^{\circ}$ slope for 80.0 ft before taking off from a negligibly short horizontal ramp. If the jumper's takeoff speed is $45.0 \mathrm{ft} / \mathrm{s},$ what is the coefficient of kinetic friction between skis and slope? Would the value of the coefficient of friction be different if expressed in SI units? If yes, by how much would it differ?
At sea level, a nitrogen molecule in the air has an average kinetic energy of $6.2 \cdot 10^{-21} \mathrm{~J}$. Its mass is $4.7 \cdot 10^{-26} \mathrm{~kg}$. If the molecule could shoot straight up without colliding with other molecules, how high would it rise? What percentage of the Earth's radius is this height? What is the molecule's initial speed? (Assume that you can use $g=9.81 \mathrm{~m} / \mathrm{s}^{2}$; although we'll see in Chapter 12 that this assumption may not be justified for this situation.)
A bullet moving at a speed of $153 \mathrm{~m} / \mathrm{s}$ passes through a plank of wood. After passing through the plank, its speed is $130 . \mathrm{m} / \mathrm{s}$. Another bullet, of the same mass and size but moving at $92.0 \mathrm{~m} / \mathrm{s}$, passes through an identical plank. What will this second bullet's speed be after passing through the plank? Assume that the resistance offered by the plank is independent of the speed of the bullet.
A particle of mass $m$ is subjected to a force acting in the $x$ -direction. $F_{x}=(3.00+0.500 x) \mathrm{N} .$ Find the work done by the force as the particle moves from $x=0.00$ to $x=4.00 \mathrm{~m}$
A force has the dependence $F_{x}(x)=-k x^{4}$ on the displacement $x$, where the constant $k=20.3 \mathrm{~N} / \mathrm{m}^{4}$. How much work does it take to change the displacement, working against the force, from $0.730 \mathrm{~m}$ to $1.35 \mathrm{~m} ?$
A body of mass $m$ moves along a trajectory $\vec{r}(t)$ in three-dimensional space with constant kinetic energy. What geometric relationship has to exist between the body's velocity vector, $\vec{v}(t),$ and its acceleration vector, $\vec{a}(t),$ in order to accomplish this?
A force given by $\vec{F}(x)=5 x^{3} \dot{x}$ (in $\mathrm{N} / \mathrm{m}^{3}$ ) acts on a $1.00-\mathrm{kg}$ mass moving on a frictionless surface. The mass moves from $x=2.00 \mathrm{~m}$ to $x=6.00 \mathrm{~m}$.a) How much work is done by the force?b) If the mass has a speed of $2.00 \mathrm{~m} / \mathrm{s}$ at $x=2.00 \mathrm{~m},$ what is its speed at $x=6.00 \mathrm{~m} ?$
An ideal spring has the spring constant $k=440 . \mathrm{N} / \mathrm{m} .$ Calculate the distance this spring must be stretched from its equilibrium position for 25.0 I of work to be done.
A spring is stretched $5.00 \mathrm{~cm}$ from its equilibrium position. If this stretching requires $30.0 \mathrm{~J}$ of work, what is the spring constant?
A spring with spring constant $k$ is initially compressed a distance $x_{0}$ from its equilibrium length. After returning to its equilibrium position, the spring is then stretched a distance $x_{0}$ from that position. What is the ratio of the work that needs to be done on the spring in the stretching to the work done in the compressing?
A spring with a spring constant of $238.5 \mathrm{~N} / \mathrm{m}$ is compressed by $0.231 \mathrm{~m}$. Then a steel ball bearing of mass $0.0413 \mathrm{~kg}$ is put against the end of the spring, and the spring is released. What is the speed of the ball bearing right after it loses contact with the spring? (The ball bearing will come off the spring exactly as the spring returns to its equilibrium position. Assume that the mass of the spring can be neglected.)
A horse draws a sled horizontally across a snow-covered field. The coefficient of friction between the sled and the snow is $0.195,$ and the mass of the sled, including the load, is $202.3 \mathrm{~kg}$. If the horse moves the sled at a constant speed of $1.785 \mathrm{~m} / \mathrm{s}$, what is the power needed to accomplish this?
A horse draws a sled horizontally on snow at constant speed. The horse can produce a power of 1.060 hp. The coefficient of friction between the sled and the snow is $0.115,$ and the mass of the sled, including the load, is $204.7 \mathrm{~kg} .$ What is the speed with which the sled moves across the snow?
While a boat is being towed at a speed of $12.0 \mathrm{~m} / \mathrm{s}$, the tension in the towline is $6.00 \mathrm{kN}$. What is the power supplied to the boat through the towline?
A car of mass $1214.5 \mathrm{~kg}$ is moving at a speed of $62.5 \mathrm{mph}$ when it misses a curve in the road and hits a bridge piling. If the car comes to rest in $0.236 \mathrm{~s}$, how much average power (in watts) is expended in this interval?
An engine expends 40.0 hp in moving a car along a level track at a speed of $15.0 \mathrm{~m} / \mathrm{s} .$ How large is the total force acting on the car in the direction opposite to the motion of the car?
A car of mass $942.4 \mathrm{~kg}$ accelerates from rest with a constant power output of 140.5 hp. Neglecting air resistance, what is the speed of the car after $4.55 \mathrm{~s} ?$
A bicyclist coasts down a $7.0^{\circ}$ slope at a steady speed of $5.0 \mathrm{~m} / \mathrm{s}$. Assuming a total mass of $75 \mathrm{~kg}$ (bicycle plus rider), what must the cyclist's power output be to pedal up the same slope at the same speed?
A small blimp is used for advertising purposes at a football game. It has a mass of $93.5 \mathrm{~kg}$ and is attached by a towrope to a truck on the ground. The towrope makes an angle of $53.3^{\circ}$ downward from the horizontal, and the blimp hovers at a constant height of $19.5 \mathrm{~m}$ above the ground. The truck moves on a straight line for $840.5 \mathrm{~m}$ on the level surface of the stadium parking lot at a constant velocity of $8.90 \mathrm{~m} / \mathrm{s}$. If the drag coefficient ( $K$ in $F=K v^{2}$ ) is $0.500 \mathrm{~kg} / \mathrm{m}$, how much work is done by the truck in pulling the blimp (assuming there is no wind)?
A car of mass $m$ accelerates from rest along a level straight track, not at a constant acceleration but with constant engine power, $P$. Assume that air resistance is negligible.a) Find the car's velocity as a function of time.b) A second car starts from rest alongside the first car on the same track. but maintains a constant acceleration. Which car takes the initial lead? Does the other car overtake it? If yes, write a formula for the distance from the starting point at which this happens.c) You are in a drag race, on a straight level track, with an opponent whose car maintains a constant acceleration of $12.0 \mathrm{~m} / \mathrm{s}^{2}$. Both cars have identical. masses of $1000 .$ kg. The cars start together from rest. Air resistance is assumed to be negligible. Calculate the minimum power your engine needs for you to win the race, assuming the power output is constant and the distance to the finish line is $0.250 \mathrm{mi}$
At the 2004 Olympic Games in Athens, Greece, the Iranian athlete Hossein Rezazadeh won the super-heavyweight class gold medal in weightlifting. He lifted $472.5 \mathrm{~kg}(1042 \mathrm{lb})$ combined in his two best lifts in the competition. Assuming that he lifted the weights a height of $196.7 \mathrm{~cm}$, what work did he do?
How much work is done against gravity in lifting a $6.00-\mathrm{kg}$ weight through a distance of $20.0 \mathrm{~cm} ?$
A certain tractor is capable of pulling with a steady force of $14.0 \mathrm{kN}$ while moving at a speed of $3.00 \mathrm{~m} / \mathrm{s}$. How much power in kilowatts and in horsepower is the tractor delivering under these conditions?
A shot-putter accelerates a $7.30-\mathrm{kg}$ shot from rest to $14.0 \mathrm{~m} / \mathrm{s}$. If this motion takes $2.00 \mathrm{~s}$, what average power was supplied?
An advertisement claims that a certain $1200 .-\mathrm{kg}$ car can accelerate from rest to a speed of $25.0 \mathrm{~m} / \mathrm{s}$ in $8.00 \mathrm{~s}$. What average power must the motor supply in order to cause this acceleration? Ignore losses due to friction.
A car of mass $m=1250 \mathrm{~kg}$ is traveling at a speed of $v_{0}=105 \mathrm{~km} / \mathrm{h}$ $(29.2 \mathrm{~m} / \mathrm{s}) .$ Calculate the work that must be done by the brakes to completely stop the car.
An arrow of mass $m=88.0 \mathrm{~g}(0.0880 \mathrm{~kg})$ is fired from a bow. The bowstring exerts an average force of $F=110 . \mathrm{N}$ on the arrow over a distance $d=78.0 \mathrm{~cm}(0.780 \mathrm{~m}) .$ Calculate the speed of the arrow as it leaves the bow.
The mass of a physics textbook is $3.40 \mathrm{~kg}$. You pick the book up off a table and lift it $0.470 \mathrm{~m}$ at a constant speed of $0.270 \mathrm{~m} / \mathrm{s}$.a) What is the work done by gravity on the book?b) What is the power you supplied to accomplish this task?
A sled, with mass $m$, is given a shove up a frictionless incline, which makes a $28.0^{\circ}$ angle with the horizontal. Eventually, the sled comes to a stop at a height of $1.35 \mathrm{~m}$ above where it started. Calculate its initial speed.
A man throws a rock of mass $m=0.325 \mathrm{~kg}$ straight up into the air. In this process, his arm does a total amount of work $W_{\mathrm{net}}=115 \mathrm{~J}$ on the rock. Calculate the maximum distance, $h$, above the man's throwing hand that the rock will travel. Neglect air resistance.
A car does the work $W_{c a r}=7.00 \cdot 10^{4} \mathrm{~J}$ in traveling a distance $x=2.80 \mathrm{~km}$ at constant speed. Calculate the average force $F$ (from all sources) acting on the car in this process.
A softball, of mass $m=0.250 \mathrm{~kg},$ is pitched at a speed $v_{0}=26.4 \mathrm{~m} / \mathrm{s}$ Due to air resistance, by the time it reaches home plate, it has slowed by $10.0 \%$. The distance between the plate and the pitcher is $d=15.0 \mathrm{~m}$. Calculate the average force of air resistance, $F_{\text {air }}$, that is exerted on the ball during its movement from the pitcher to the plate.
A flatbed truck is loaded with a stack of sacks of cement whosecombined mass is $1143.5 \mathrm{~kg}$. The coefficient of static friction between the bed of the truck and the bottom sack in the stack is $0.372,$ and the sacks are nottied down but held in place by the force of friction between the bed and the bottom sack. The truck accelerates uniformly from rest to $56.6 \mathrm{mph}$ in $22.9 \mathrm{~s}$. The stack of sacks is $1 \mathrm{~m}$ from the end of the truck bed. Does the stack slide on the truck bed? The coefficient of kinetic friction between the bottom sackand the truck bed is $0.257 .$ What is the work done on the stack by the force of friction between the stack and the bed of the truck?
A driver notices that her $1000 .-\mathrm{kg}$ car slows from $v_{0}=90.0 \mathrm{~km} / \mathrm{h}$ $(25.0 \mathrm{~m} / \mathrm{s})$ to $v=70.0 \mathrm{~km} / \mathrm{h}(19.4 \mathrm{~m} / \mathrm{s})$ in $t=6.00 \mathrm{~s}$ moving on level groundin neutral gear. Calculate the power needed to keep the car moving at a constant speed, $v_{\text {ave }}=80.0 \mathrm{~km} / \mathrm{h}(22.2 \mathrm{~m} / \mathrm{s})$. Assume that energy is lost at a constant rate during the deceleration.
The 125 -kg cart in the figure starts from rest and rolls with negligible friction. It is pulled by three ropes as shown. It moves $100 .$ m horizontally. Find the final velocity of the cart.
Calculate the power required to propel a $1000.0-\mathrm{kg}$ car at $25.0 \mathrm{~m} / \mathrm{s}$ up a straight slope inclined $5.00^{\circ}$ above the horizontal. Neglect friction and air resistance.
A grandfather pulls his granddaughter, whose mass is $21.0 \mathrm{~kg}$ and who is sitting on a swing with ropes of length $2.50 \mathrm{~m}$, backward and releases her from rest. The speed of the granddaughter at the bottom of the swinging motion is $3.00 \mathrm{~m} / \mathrm{s}$. What is the angle (in degrees, measured relative to the vertical) from which she is released?
A 65 -kg hiker climbs to the second base camp on Nanga Parbat in Pakistan, at an altitude of $3900 \mathrm{~m}$, starting from the first base camp at $2200 \mathrm{~m}$. The climb is made in $5.0 \mathrm{~h}$. Calculate (a) the work done against gravity,(b) the average power output, and (c) the rate of energy input required, assuming the energy conversion efficiency of the human body is $15 \%$.
An $x$ -component of a force has the dependence $F_{x}(x)=-c x^{3}$ on the displacement $x$, where the constant $c=19.1 \mathrm{~N} / \mathrm{m}^{3} .$ How much work does it take to oppose this force and change the displacement from $0.810 \mathrm{~m}$ to $1.39 \mathrm{~m} ?$
A massless spring lying on a smooth horizontal surface is compressed by a force of $63.5 \mathrm{~N}$, which results in a displacement of $4.35 \mathrm{~cm}$ from the initial equilibrium position. How much work will it take to compress the spring from $4.35 \mathrm{~cm}$ to $8.15 \mathrm{~cm} ?$
A car is traveling at a constant speed of $26.8 \mathrm{~m} / \mathrm{s}$. It has a drag coefficient $c_{\mathrm{d}}=0.333$ and a cross-sectional area of $3.25 \mathrm{~m}^{2} .$ How much power is required just to overcome air resistance and keep the car traveling at this constant speed? Assume the density of air is $1.15 \mathrm{~kg} / \mathrm{m}^{3}$.
A variable force is given by $F(x)=A x^{6},$ where $A=11.45 \mathrm{~N} / \mathrm{m}^{6}$. This force acts on an object of mass 2.735 kg that moves on a frictionless surface. Starting from rest, the object moves from $x=1.093 \mathrm{~m}$ to $x=4.429 \mathrm{~m}$. How much does the kinetic energy of the object change?
A variable force is given by $F(x)=A x^{6},$ where $A=13.75 \mathrm{~N} / \mathrm{m}^{6} .$ This force acts on an object of mass $3.433 \mathrm{~kg}$ that moves on a frictionless surface. Starting from rest, the object moves from $x=1.105 \mathrm{~m}$ to a new position, $x$. The object gains $5.662 \cdot 10^{3} \mathrm{~J}$ of kinetic energy. What is the new position $x ?$
A variable force is given by $F(x)=A x^{6},$ where $A=16.05 \mathrm{~N} / \mathrm{m}^{6} .$ This force acts on an object of mass $3.127 \mathrm{~kg}$ that moves on a frictionless surface. Starting from rest, the object moves from a position $x_{0}$ to a new position, $x=3.313 \mathrm{~m}$. The object gains $1.00396 \cdot 10^{4} \mathrm{~J}$ of kinetic energy. What is the initial position $x_{0}$ ?
Santa's reindeer pull his sleigh through the snow at a speed of $3.333 \mathrm{~m} / \mathrm{s}$. The mass of the sleigh, including Santa and the presents, is $537.3 \mathrm{~kg}$. Assuming that the coefficient of kinetic friction between the runners of the sleigh and the snow is $0.1337,$ what is the total power (in hp) that the reindeer are providing?
Santa's reindeer pull his sleigh through the snow at a speed of $2.561 \mathrm{~m} / \mathrm{s}$ The mass of the sleigh, including Santa and the presents, is $540.3 \mathrm{~kg} .$ Assuming that the reindeer can provide a total power of $2.666 \mathrm{hp}$, what is the coefficient of friction between the runners of the sleigh and the snow?
Santa's reindeer pull his sleigh through the snow at a speed of $2.791 \mathrm{~m} / \mathrm{s}$. Assuming that the reindeer can provide a total power of 3.182 hp and the coefficient of friction between the runners of the sleigh and the snow is $0.1595,$ what is the mass of the sleigh, including Santa and the presents?
A horizontal spring with spring constant $k=15.19 \mathrm{~N} / \mathrm{m}$ is compressed $23.11 \mathrm{~cm}$ from its equilibrium position. A hockey puck with mass $m=170.0 \mathrm{~g}$ is placed against the end of the spring. The spring is released, and the puck slides on horizontal ice, with a coefficient of kinetic friction of 0.02221 between the puck and the ice. How far does the hockey puck travel on the ice after it leaves the spring?
A horizontal spring with spring constant $k=17.49 \mathrm{~N} / \mathrm{m}$ is compressed $23.31 \mathrm{~cm}$ from its equilibrium position. A hockey puck with mass $m=170.0 \mathrm{~g}$ is placed against the end of the spring. The spring is released, and the puck slides on horizontal ice a distance of $12.13 \mathrm{~m}$ after it leaves the spring. What is the coefficient of kinetic friction between the puck and the ice?
A load of bricks at a construction site has a mass of $75.0 \mathrm{~kg}$. A crane raises this load from the ground to a height of $45.0 \mathrm{~m}$ in $52.0 \mathrm{~s}$ at a low constant speed. What is the average power of the crane?
A load of bricks at a construction site has a mass of $75.0 \mathrm{~kg}$. A crane with 725 W of power raises this load from the ground to a height of $45.0 \mathrm{~m}$ at a low constant speed. How long does it take to raise the load?
A load of bricks at a construction site has a mass of $75.0 \mathrm{~kg} .$ A crane with $815 \mathrm{~W}$ of power raises this load from the ground to a certain height in $52.0 \mathrm{~s}$ at a low constant speed. What is the final height of the load?