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Physics 101 Mechanics Q&A Archive of December 3, 2021

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December 3 of 2021

An engineer claims that flow of SAE 30W oil, at 20?C, through a 5-cm-diametersmooth pipe at 1 million N/h, is laminar. Do you agree? A million newton’s is a lot, so this sounds like an awfully high flow rate.
The small turbine in shown below extracts 400 W of power from the water flow. Both pipes are wrought iron. Compute the flow rate Q m3 /h. Why are there two solutions? Which is better and why?
a 3520 kg truck moving north at 18.5 m/s makes an INELASTIC collision with an 1480 kg car moving east after colliding they have a velocity of 13.6 m/s at 72.6 degrees what was the initial velocity of the car
6. The thermal emissivity of human skin is approximately 0.915 and the average surface area of a person is 1.78 m2. This average person is standing inside an air-conditioned room eating a 280 Cal ice-cream cone. The person’s skin temperature is 37.2?C and the temperature of the surroundings…
A train starts from rest and accelerate uniformly at the rate of 5 m/s2 for 5 sec. Calculate the velocity of train in 5 sec.
A scooter travelling at 10 m/s speed up to 20 m/s in 4 sec. Find the acceleration of scooter.
A truck travelling at 54 km/h is slow down to 36 km/h in 10 sec. Find the retardation
A body whose speed is constant (a) Must be accelerated (b) Might be accelerated (c) Has a constant velocity (d) Cannot be accelerated
A train accelerates from 36 km/h to 54 km/h in 10 sec. (ii) The distance travelled by car.
A train accelerates from 36 km/h to 54 km/h in 10 sec. (i) Acceleration
At the top of the trajectory of a projectile, the directions of its velocity and acceleration are A) Perpendicular to each other B) Parallel to each other C) Inclined to each other at an angle of 45o D) Antiparallel to each other
A ball is thrown upwards and it returns to ground describing a parabolic path. Which of the following remains constant [BHU 1999; DPMT 2001; AMU (Engg.) 2000] A) Kinetic energy of the ball B) Speed of the ball C) Horizontal…
The range of a projectile for a given initial velocity is maximum when the angle of projection is 45o. The range will be minimum, if the angle of projection is
If the initial velocity of a projectile be doubled, keeping the angle of projection same, the maximum height reached by it will
A projectile fired with initial velocity u at some angle ? has a range R. If the initial velocity be doubled at the same angle of projection, then the range will be
An object is thrown along a direction inclined at an angle of 45o with the horizontal direction. The horizontal range of the particle is equal to A) Vertical height B) Twice the vertical height C) Thrice the vertical height D) Four…
Vector a = 3 units ,acting along east, and vector b = 4 units , acting along north. What is the magnitude of their resultant ?
What is the direction of velocity of a particle in a uniform circular motion?
The horizontal and vertical component of a vector are 3 units and 4 units respectively. What is the magnitude of the vector
A vector of 10 units acts at a point making an angle 0with the horizontal . what are the horizontal and vertical components of the vector ?
A vector of 10 units acts at a point making an angle 30 with the horizontal . what are the horizontal and vertical components of the vector ?
What is the magnitude of v=3i+2J
A boy of mass 50 kg climbs up a vertical height of 100 m. Calculate the amount of potential energy he gains.
An object of mass mwhen raised To height h possess a potential energy of 1200 J. Find the new potential energy : (b) if the same object is raised to height 4h.
An object of mass mwhen raised To height h possess a potential energy of 1200 J. Find the new potential energy : (a) if the same object is raised to height h/4.
Two bodies of masses m, and m2 have equal kinetic energies. What is the ratio of their linear momenta?
Can a body have energy without having momentum ? Explain.
A light and a heavy body have the same momentum. Which one will have greater kinetic energy ?
As shown in fig, three forces A, B and C with equal magnitude of 50.0N act at the same point on the object. All forces are in the plane of the paper. What is the net torque about pivot point P ?
A light body and a heavy body have the same kinetic energy. Which one will have the greater momentum ?
Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her ? Why ?
A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not ? justify your answer.
A mass of 10 kg is at a point A on a table. It is moved to a point B. If the line joining A and B is horizontal, what is the work done on the object by the gravitational force?
The potential energy of a freely falling object decreases progressively. Does this violate the law of conservation of energy? Why?
What is the work done by the force of gravity in the following cases ? A stone of mass 250 g is thrown up through a height of 2.5 m.
State the relation between kW h and joule. Define 1 watt.
What is the work done by the force of gravity in the following cases ? (a) Satellite moving around the earth in a circular orbit of radius 35000 km
Can a body possess energy even if it is not in motion ?
By how much will the speed of a body, of fixed mass, increase if its kinetic energy becomes four times its initial kinetic energy ?
What will happen to the kinetic energy of a body if its mass is doubled ?
What will happen to the kinetic energy of a body if its velocity is halved ?
Does a body at rest possess any kinetic energy ?
A lamp consumes 100 J of electrical energy in 5s. What is its power ?
A lamp consumes 1000 J of electrical energy in 10 s. What is its power ?
Define 1 watt of power.
A pair of bullocks exert a force of 140 N on a plough. The field being ploughed is 15 m long. How much work is done in ploughing the length of the field ?
A force of 7 N acts on an object. The displacement is, say 8 m, in the direction of the force. Let us take it that the force acts on the object through the displacement. What is the work done in this case ?
A step index fiber is made with a core of refractive index 1.52, a diameter of 49µm and a fractional refractive index change of 0.0007.It is operated at a wavelength of 1.3µm. Find the normalized frequency of the fiber.
Can a fire have a shadow?
How many minutes does it take light from Proxima Centauri (4.0x 10^16m) to reach us?
The figure shows particles 1 and 2, each of mass m, attached to the ends of a rigid massless rod of length L1 + L2, with L1 = 3.0 m and L2 = 6.0 m. The rod is held horizontally on the fulcrum and then released. What is the magnitude of the angular acceleration of the system?
At t=0, a disk has an angular velocity of 360 rev/min, and constant angular acceleration of -0.50 rad/s2. How many rotations does the disk make before coming to rest?
Force F = (2.0N)i - (3.0N)k acts on a pebble (small stone) with position vectorr = (0.5m)i - (2.0m)k relative to the origin. Find the magnitude of the resulting torque on the pebble about the point (2.0 m, 0, ?3.0 m).
A FOUNTAIN FROM WHICH WATER RUSHES VERTICALLY AT AN INITIAL SPEED(14.7m/s) neglecting air resistance consider the free falling wheel (10m/s²)
Problem 5Medium DifficultyRaising a Ladder. A ladder carried by a fire truck is 20.0 long. The ladder weighs 2800 and its center of gravity is at its center. The ladder is pivoted at one end about a pin (Fig. E11.5); you can ignore the friction torque at the pin. The ladder is raised into…
Four identical particles, each with mass m, are arranged in the x, y plane as shown in Fig. They are connected by light sticks of negligible mass to form a rigid body. If m = 2.0 kg and a = 1.0 m, the rotational inertia of this system about the y-axis is
A ladder carried by a fire truck is 20.0 m long. The ladder weighs 3400 N and its center of gravity is at its center. The ladder is pivoted at one end () about a pin (); ignore the friction torque at the pin. The ladder is raised into position by a force applied by a hydraulic piston at . Point…
Two wheels A and B are identical. Wheel B is rotating with twice the angular velocity of wheel A. The ratio of the radial acceleration of a point on the rim of B (a2) to the radial acceleration of a point on the rim of A (a1) is (a2/a1) :
A ladder carried by a firetruck is 20.0 cm long. The ladder weighs 2800 N and its center of gravity is at its center. The ladder is pivoted at one end (A) about a pin (shown in figure below); you can ignore the friction torque at the pin. The ladder is raised into position by a force applied by…
Calculate the rotational inertia of a wheel that has a kinetic energy of 35.6 kJ when rotating at 361 rev/min
The center of gravity of an irregular object is shown in figure below. You need to move the center of gravity 2.20 cm to the left by gluing on a tiny 1.50 kg mass, which will then be considered as part of the object. Where would you attach the additional mass?
I need help with the question on the image
In the figure, two forces F1 and F2 act on a disk that turns about its center like a merrygo-round. The forces maintain the indicated angles during the rotation, which is counterclockwise and at a constant rate. However, we are to decrease the angle θ without changing the magnitude of F1. i).…
A 2.40 kg, 50.0 cm long uniform bar has a small 1.10 kg mass glued to its left end and a small 2.20 kg mass glued to the other end. You want to balance this system horizontally on a fulcrum placed just under its center of gravity. How far from the left end should the fulcrum be placed?
The cable stays AB and AD help support pole AC. Knowing that the tension is 120 lb in AB and 40 lb in AD, determine graphically the magnitude and direction of the resultant of the forces exerted by the stays at A using (a) the parallelogram law, (b) the triangle rule.
?n the setup g?ven ?n the f?gure, the horizontalvertical surfaces are fr?ctional and the system is in equilibrium. calculate the support react?ons and the M value.
hatched area given in the figure a-) f?nd the center of gravity coordinates according to given x-y axes. b-) calculate the volume of the body rotated around x-axis.
self weight of given plate in the figure is 10 ton and the system is in equilibrium calculate A,B,C support reactions
difference between vectors and stairs
A person drags a box at constant velocity through a horizontal distance of 5.00 m by exerting a 200.0 N force at 30.0 degrees with the horizontal. Hint: Draw a FBD. a) How much work does the man do on the box? (1) b) How much work does the friction force do on the box? (2)
Determine the minimum coefficient of static friction between the tires and the road for a 1,684 kg car if the car makes a turn at 120 km/h with a radius of curvature of 125 m.
A 43 kg child is on a roller coaster ride. At the beginning of a large dip in the track they are 25.7 m above the ground and have a velocity of 1.10 m/s. How high above the ground will they be when their velocity reaches 10.1 m/s. Assume no energy losses due to friction or air resistance.
The displacement (in meters) of a wave is given according to y = 0.341 sin (?t - 3.26 x), where t is in seconds and x is in meters. What is the displacement (in m) y when t = 47.3 s and x = 12.6 m?
An engineer claims that flow of SAE 30W oil, at 20?C, through a 5-cm-diametersmooth pipe at 1 million N/h, is laminar. Do you agree? A million newton’s is a lot, so this sounds like an awfully high flow rate.
6. The thermal emissivity of human skin is approximately 0.915 and the average surface area of a person is 1.78 m2. This average person is standing inside an air-conditioned room eating a 280 Cal ice-cream cone. The person’s skin temperature is 37.2?C and the temperature of the surroundings…
A train starts from rest and accelerate uniformly at the rate of 5 m/s2 for 5 sec. Calculate the velocity of train in 5 sec.
A scooter travelling at 10 m/s speed up to 20 m/s in 4 sec. Find the acceleration of scooter.
A truck travelling at 54 km/h is slow down to 36 km/h in 10 sec. Find the retardation
A body whose speed is constant (a) Must be accelerated (b) Might be accelerated (c) Has a constant velocity (d) Cannot be accelerated
A train accelerates from 36 km/h to 54 km/h in 10 sec. (ii) The distance travelled by car.
A train accelerates from 36 km/h to 54 km/h in 10 sec. (i) Acceleration
At the top of the trajectory of a projectile, the directions of its velocity and acceleration are A) Perpendicular to each other B) Parallel to each other C) Inclined to each other at an angle of 45o D) Antiparallel to each other
A ball is thrown upwards and it returns to ground describing a parabolic path. Which of the following remains constant [BHU 1999; DPMT 2001; AMU (Engg.) 2000] A) Kinetic energy of the ball B) Speed of the ball C) Horizontal…
The range of a projectile for a given initial velocity is maximum when the angle of projection is 45o. The range will be minimum, if the angle of projection is
If the initial velocity of a projectile be doubled, keeping the angle of projection same, the maximum height reached by it will
A projectile fired with initial velocity u at some angle ? has a range R. If the initial velocity be doubled at the same angle of projection, then the range will be
An object is thrown along a direction inclined at an angle of 45o with the horizontal direction. The horizontal range of the particle is equal to A) Vertical height B) Twice the vertical height C) Thrice the vertical height D) Four…
Vector a = 3 units ,acting along east, and vector b = 4 units , acting along north. What is the magnitude of their resultant ?
What is the direction of velocity of a particle in a uniform circular motion?
The horizontal and vertical component of a vector are 3 units and 4 units respectively. What is the magnitude of the vector
A vector of 10 units acts at a point making an angle 0with the horizontal . what are the horizontal and vertical components of the vector ?
A vector of 10 units acts at a point making an angle 30 with the horizontal . what are the horizontal and vertical components of the vector ?
What is the magnitude of v=3i+2J
A boy of mass 50 kg climbs up a vertical height of 100 m. Calculate the amount of potential energy he gains.
An object of mass mwhen raised To height h possess a potential energy of 1200 J. Find the new potential energy : (b) if the same object is raised to height 4h.
An object of mass mwhen raised To height h possess a potential energy of 1200 J. Find the new potential energy : (a) if the same object is raised to height h/4.
Two bodies of masses m, and m2 have equal kinetic energies. What is the ratio of their linear momenta?
Can a body have energy without having momentum ? Explain.
A light and a heavy body have the same momentum. Which one will have greater kinetic energy ?
As shown in fig, three forces A, B and C with equal magnitude of 50.0N act at the same point on the object. All forces are in the plane of the paper. What is the net torque about pivot point P ?
A light body and a heavy body have the same kinetic energy. Which one will have the greater momentum ?
Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her ? Why ?
A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not ? justify your answer.
A mass of 10 kg is at a point A on a table. It is moved to a point B. If the line joining A and B is horizontal, what is the work done on the object by the gravitational force?
The potential energy of a freely falling object decreases progressively. Does this violate the law of conservation of energy? Why?
What is the work done by the force of gravity in the following cases ? A stone of mass 250 g is thrown up through a height of 2.5 m.
State the relation between kW h and joule. Define 1 watt.
What is the work done by the force of gravity in the following cases ? (a) Satellite moving around the earth in a circular orbit of radius 35000 km
Can a body possess energy even if it is not in motion ?
By how much will the speed of a body, of fixed mass, increase if its kinetic energy becomes four times its initial kinetic energy ?
What will happen to the kinetic energy of a body if its mass is doubled ?
What will happen to the kinetic energy of a body if its velocity is halved ?
Does a body at rest possess any kinetic energy ?
A lamp consumes 100 J of electrical energy in 5s. What is its power ?
A lamp consumes 1000 J of electrical energy in 10 s. What is its power ?
Define 1 watt of power.
A pair of bullocks exert a force of 140 N on a plough. The field being ploughed is 15 m long. How much work is done in ploughing the length of the field ?
A force of 7 N acts on an object. The displacement is, say 8 m, in the direction of the force. Let us take it that the force acts on the object through the displacement. What is the work done in this case ?
Can a fire have a shadow?
The figure shows particles 1 and 2, each of mass m, attached to the ends of a rigid massless rod of length L1 + L2, with L1 = 3.0 m and L2 = 6.0 m. The rod is held horizontally on the fulcrum and then released. What is the magnitude of the angular acceleration of the system?
At t=0, a disk has an angular velocity of 360 rev/min, and constant angular acceleration of -0.50 rad/s2. How many rotations does the disk make before coming to rest?
Force F = (2.0N)i - (3.0N)k acts on a pebble (small stone) with position vectorr = (0.5m)i - (2.0m)k relative to the origin. Find the magnitude of the resulting torque on the pebble about the point (2.0 m, 0, ?3.0 m).
A FOUNTAIN FROM WHICH WATER RUSHES VERTICALLY AT AN INITIAL SPEED(14.7m/s) neglecting air resistance consider the free falling wheel (10m/s²)
Four identical particles, each with mass m, are arranged in the x, y plane as shown in Fig. They are connected by light sticks of negligible mass to form a rigid body. If m = 2.0 kg and a = 1.0 m, the rotational inertia of this system about the y-axis is
Two wheels A and B are identical. Wheel B is rotating with twice the angular velocity of wheel A. The ratio of the radial acceleration of a point on the rim of B (a2) to the radial acceleration of a point on the rim of A (a1) is (a2/a1) :
Calculate the rotational inertia of a wheel that has a kinetic energy of 35.6 kJ when rotating at 361 rev/min
I need help with the question on the image
In the figure, two forces F1 and F2 act on a disk that turns about its center like a merrygo-round. The forces maintain the indicated angles during the rotation, which is counterclockwise and at a constant rate. However, we are to decrease the angle θ without changing the magnitude of F1. i).…
The cable stays AB and AD help support pole AC. Knowing that the tension is 120 lb in AB and 40 lb in AD, determine graphically the magnitude and direction of the resultant of the forces exerted by the stays at A using (a) the parallelogram law, (b) the triangle rule.
?n the setup g?ven ?n the f?gure, the horizontalvertical surfaces are fr?ctional and the system is in equilibrium. calculate the support react?ons and the M value.
hatched area given in the figure a-) f?nd the center of gravity coordinates according to given x-y axes. b-) calculate the volume of the body rotated around x-axis.
self weight of given plate in the figure is 10 ton and the system is in equilibrium calculate A,B,C support reactions
difference between vectors and stairs
A person drags a box at constant velocity through a horizontal distance of 5.00 m by exerting a 200.0 N force at 30.0 degrees with the horizontal. Hint: Draw a FBD. a) How much work does the man do on the box? (1) b) How much work does the friction force do on the box? (2)
Determine the minimum coefficient of static friction between the tires and the road for a 1,684 kg car if the car makes a turn at 120 km/h with a radius of curvature of 125 m.
A 43 kg child is on a roller coaster ride. At the beginning of a large dip in the track they are 25.7 m above the ground and have a velocity of 1.10 m/s. How high above the ground will they be when their velocity reaches 10.1 m/s. Assume no energy losses due to friction or air resistance.
The displacement (in meters) of a wave is given according to y = 0.341 sin (?t - 3.26 x), where t is in seconds and x is in meters. What is the displacement (in m) y when t = 47.3 s and x = 12.6 m?