University Physics with Modern Physics

Wolfgang Bauer, Gary D. Westfall

Chapter 5

Kinetic Energy Work and Power - all with Video Answers

Educators

Chapter Questions

Problem 1

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) $\mathrm{kg}^{2} \mathrm{~m} / \mathrm{s}^{2}$

Shahab Ullah

Shahab Ullah

Numerade Educator

Problem 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) $0 \mathrm{~N}$
c) greater than $400 \mathrm{~N}$
b) not zero but
d) $400 \mathrm{~N}$
less than $400 \mathrm{~N}$ e) $800 \mathrm{~N}$

Averell Hause

Carnegie Mellon University

Problem 3

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 kinetic energy being imparted to the water?
a) $\frac{1}{2} k v^{3}$
c) $\frac{1}{2} k v$
e) $\frac{1}{2} v^{3} / k$
b) $\frac{1}{2} k v^{2}$
d) $\frac{1}{2} v^{2} / k$

Prabhu Ramji

Numerade Educator

Problem 4

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) $60 \mathrm{hp}$
c) $80 \mathrm{hp}$
e) $180 \mathrm{hp}$
b) $70 \mathrm{hp}$
d) $90 \mathrm{hp}$

Shahab Ullah

Numerade Educator

Problem 5

Which of the following is a correct unit of power?
a) $\mathrm{kg} \mathrm{m} / \mathrm{s}^{2}$
c) J
e) $W$
b) $N$
d) $\mathrm{m} / \mathrm{s}^{2}$

Shahab Ullah

Numerade Educator

Problem 6

How much work is done when a $75-\mathrm{kg}$ person climbs a flight of stairs $10 \mathrm{~m}$ high at constant speed?
a) $7.35 \cdot 10^{5}$ J
c) 75
e) 7350 J
b) 750 J
d) 7500 J

Shahab Ullah

Numerade Educator

Problem 7

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 J
c) $1.3 \cdot 10^{4}$ ]
e) 130 ]
b) 1845 J
d) $1.8 \cdot 10^{4}$ ]

Shahab Ullah

Numerade Educator

Problem 8

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 J
c) 230
e) 14
b) 23 J
d) 0.81

Shahab Ullah

Numerade Educator

Problem 9

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 J
c) $30 J$
e) 120 J
b) 15 J
d) 60

Shahab Ullah

Numerade Educator

Problem 10

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.

Prabhu Ramji

Numerade Educator

Problem 11

If the net work done on a particle is zero, what can be said about the particle's speed?

Shahab Ullah

Numerade Educator

Problem 12

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?

Ajay Singhal

Numerade Educator

Problem 13

Does the Earth do any work on the Moon as the Moon moves in its orbit?

Shahab Ullah

Numerade Educator

Problem 14

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 $2, v_{2}=2 v_{1},$ by what factor is its stopping distance increased, assuming that the braking force $F$ is approximately independent of the car's speed?

Prabhu Ramji

Numerade Educator

Problem 15

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 $100.0 \mathrm{~g}$ baseball at $60.0 \mathrm{~m} / \mathrm{s}$
c) a $20.0 \mathrm{~g}$ bullet at $300 . \mathrm{m} / \mathrm{s}$

Shahab Ullah

Numerade Educator

Problem 16

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?

Shahab Ullah

Numerade Educator

Problem 17

Two railroad cars, each of mass $7000 . \mathrm{kg}$ 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?

Shahab Ullah

Numerade Educator

Problem 18

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?

Shahab Ullah

Numerade Educator

Problem 19

A $200 .-\mathrm{kg}$ moving tiger has a kinetic energy of $14,400 \mathrm{~J}$ What is the speed of the tiger?

Shahab Ullah

Numerade Educator

Problem 20

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 $5.0 \mathrm{~m} / \mathrm{s}$, they then have the same kinetic energy, Calculate the original speeds of the two cars.

Prabhu Ramji

Numerade Educator

Problem 21

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?

Prabhu Ramji

Numerade Educator

Problem 22

A force of $5.00 \mathrm{~N}$ acts through a distance of $12.0 \mathrm{~m}$ in the direction of the force. Find the work done.

Shahab Ullah

Numerade Educator

Problem 23

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 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.)

Prabhu Ramji

Numerade Educator

Problem 24

A $95-\mathrm{kg}$ refrigerator rests on the floor. How much work is required to move it at constant speed for $4.0 \mathrm{~m}$ along the floor against a friction force of $180 \mathrm{~N} ?$

Ankur S

Numerade Educator

Problem 25

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.

Shahab Ullah

Numerade Educator

Problem 26

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?

Prabhu Ramji

Numerade Educator

Problem 27

Supppose 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 $25.0 \mathrm{~m} ?$

Shahab Ullah

Numerade Educator

Problem 28

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?

Prabhu Ramji

Numerade Educator

Problem 29

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?

Prabhu Ramji

Numerade Educator

Problem 30

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?

Prabhu Ramji

Numerade Educator

Problem 31

A ski jumper glides down a $30.0^{\circ}$ slope for $80.0 \mathrm{ft}$ 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?

Prabhu Ramji

Numerade Educator

Problem 32

At sea level, a nitrogen molecule in the air has an average kinetic energy of $6.2 \cdot 10^{-21}$ 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.

Prabhu Ramji

Numerade Educator

Problem 33

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 $92 \mathrm{~m} / \mathrm{s}$, 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.

Prabhu Ramji

Numerade Educator

Problem 34

A particle of mass $m$ is subjected to a force acting in the $x$ -direction. $F_{x}=(3.0+0.50 x) \mathrm{N}$. Find the work done by the force as the particle moves from $x=0$ to $x=4.0 \mathrm{~m}$

Shahab Ullah

Numerade Educator

Problem 35

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 from $0.73 \mathrm{~m}$ to $1.35 \mathrm{~m} ?$

Shahab Ullah

Numerade Educator

Problem 36

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

Prabhu Ramji

Numerade Educator

Problem 37

A force given by $F(x)=5 x^{3} \hat{x}\left(\right.$ in $\left.\mathrm{N} / \mathrm{m}^{3}\right)$ 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 $x=6.00 \mathrm{~m} ?$

Prabhu Ramji

Numerade Educator

Problem 38

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 J of work to be done.

Shahab Ullah

Numerade Educator

Problem 39

A spring is stretched $5.00 \mathrm{~cm}$ from its equilibrium position. If this stretching requires 30.0 J of work, what is the spring constant?

Prabhu Ramji

Numerade Educator

Problem 40

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?

Prabhu Ramji

Numerade Educator

Problem 41

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.)

Prabhu Ramji

Numerade Educator

Problem 42

A horse draws a sled horizontally across a snowcovered 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?

Averell Hause

Carnegie Mellon University

Problem 43

A horse draws a sled horizontally on snow at constant speed. The horse can produce a power of $1.060 \mathrm{hp} .$ 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?

Prabhu Ramji

Numerade Educator

Problem 44

While a boat is being towed at a speed of $12 \mathrm{~m} / \mathrm{s}$, the tension in the towline is $6.0 \mathrm{kN}$. What is the power supplied to the boat through the towline?

Prabhu Ramji

Numerade Educator

Problem 45

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?

Prabhu Ramji

Numerade Educator

Problem 46

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 opposite direction of the motion of the car?

Prabhu Ramji

Numerade Educator

Problem 47

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?

Prabhu Ramji

Numerade Educator

Problem 48

A car of mass 942.4 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 s?

Prabhu Ramji

Numerade Educator

Problem 49

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 $\left(K\right.$ in $\left.F=K v^{2}\right)$ is $0.500 \mathrm{~kg} / \mathrm{m}$, how much work is done by the truck in pulling the blimp (assuming there is no wind)?

Prabhu Ramji

Numerade Educator

Problem 50

A car of mass $m$ accelerates from rest along a level straight track, not at 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 $1000 . \mathrm{kg} .$ 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 $0.250 \mathrm{mi}$

Sai Chaitanya Tadepalli

Sai Chaitanya Tadepalli

Numerade Educator

Problem 51

At the 2004 Olympics Games in Athens, Greece, the Iranian athlete Hossein Reza Zadeh won the super-heavyweight class gold medal in weightlifting. He lifted $472.5 \mathrm{~kg}$ ( 1041 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?

Shahab Ullah

Numerade Educator

Problem 52

How much work is done against gravity in lifting a $6.00-\mathrm{kg}$ weight through a distance of $20.0 \mathrm{~cm} ?$

Prabhu Ramji

Numerade Educator

Problem 53

A certain tractor is capable of pulling with a steady force of $14 \mathrm{kN}$ while moving at a speed of $3.0 \mathrm{~m} / \mathrm{s}$. How much power in kilowatts and in horsepower is the tractor delivering under these conditions?

Shahab Ullah

Numerade Educator

Problem 54

A shot-putter accelerates a $7.3-\mathrm{kg}$ shot from rest to $14 \mathrm{~m} / \mathrm{s} .$ If this motion takes $2.0 \mathrm{~s}$, what average power was supplied?

Shahab Ullah

Numerade Educator

Problem 55

An advertisement claims that a certain $1200-\mathrm{kg}$ car can accelerate from rest to a speed of $25 \mathrm{~m} / \mathrm{s}$ in $8.0 \mathrm{~s}$. What average power must the motor supply in order to cause this acceleration? Ignore losses due to friction.

Prabhu Ramji

Numerade Educator

Problem 56

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.

Prabhu Ramji

Numerade Educator

Problem 57

An arrow of mass $m=88 \mathrm{~g}(0.088 \mathrm{~kg})$ is fired from a bow. The bowstring exerts an average force of $F=110 \mathrm{~N}$ on the arrow over a distance $d=78 \mathrm{~cm}(0.78 \mathrm{~m})$
Calculate the speed of the arrow as it leaves the bow.

Shahab Ullah

Numerade Educator

Problem 58

The mass of a physics textbook is $3.4 \mathrm{~kg}$. You pick the book up off a table and lift it $0.47 \mathrm{~m}$ at a constant speed of $0.27 \mathrm{~m} / \mathrm{s}$
a) What is the work done by gravity on the book?
b) What is the power you supplied to accomplish this task?

Shahab Ullah

Numerade Educator

Problem 59

A sled, with mass $m,$ is given a shove up a frictionless incline, which makes a $28^{\circ}$ 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.

Prabhu Ramji

Numerade Educator

Problem 60

5.60 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 $W_{\text {net }}=115 \mathrm{~J}$ on the rock. Calculate the maximum distance, $h$, above the man's throwing hand that the rock will travel.

Shahab Ullah

Numerade Educator

Problem 61

A car does the work $W_{\text {car }}=7.0 \cdot 10^{4} \mathrm{~J}$ in traveling a distance $x=2.8 \mathrm{~km}$ at constant speed. Calculate the average force $F$ (from all sources) acting on the car in this process.

Shahab Ullah

Numerade Educator

Problem 62

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.

Prabhu Ramji

Numerade Educator

Problem 63

A flatbed truck is loaded with a stack of sacks of cement whose combined 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 not tied 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 sack and 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?

Prabhu Ramji

Numerade Educator

Problem 64

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 ground in neutral gear. Calculate the power needed to keep the car moving at a constant speed, $v_{\text {ave }}=$ $80.0 \mathrm{~km} / \mathrm{h}(22.2 \mathrm{~m} / \mathrm{s})$

Averell Hause

Carnegie Mellon University

Problem 65

The $125-\mathrm{kg}$ cart in the figure starts from rest and rolls with negligible friction. It is pulled by three ropes as shown. It moves $100 . \mathrm{m}$ horizontally. Find the final velocity of the cart.

Prabhu Ramji

Numerade Educator

Problem 66

Calculate the power required to propel a $1000.0-\mathrm{kg}$ car at $25.0 \mathrm{~m} / \mathrm{s}$ up a straight slope inclined $5.0^{\circ}$ above the horizontal. Neglect friction and air resistance.

Prabhu Ramji

Numerade Educator

Problem 67

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?

Prabhu Ramji

Numerade Educator

Problem 68

A $65-\mathrm{kg}$ 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 $15 \%$

Prabhu Ramji

Numerade Educator