Zero Work

Q.

Work done by air when it expands from 50 litres to 150 litres at a constant pressure of 2 atmosphere is

1. 

2. 

3. 

4. 

Q.

A body moves a distance of 10 m along a straight line under the action of a force of 5 N. If the work done is 25 joule, the angle which the force makes with the direction of motion of the body is

1. 30°

2. 0°

3. 90°

4. 60°

Q.

A gardener pushes a lawn roller through a distance $20m$. If he applies a force of $20kg-w$t in a direction inclined at ${60}^o$ to the ground, the work done by him is

1. 1960 J

2. 196 J

3. 1.96 J

4. 196 KJ

Q. 16. Calculate the work done in pulling an object with a constant force F as shown in figure, so that the block moves with a constant velocity through a distance d(given that the ground is rough with a certain coefficient of friction)

Q. Work done by frictional force depends upon path taken since it is a non conservative force, but still we use displacement while finding out the work done( by friction) . Why is it so?

Q.

A boy pulls a toy with a force of$50N$using a string which makes an angle of ${30}^o$ with the horizontal so as to move the toy by a distance of $1m$ horizontally. If the string was inclined to make an angle of $45°$with the horizontal, how much pull would he apply along the string in order to move it is the same distance of $1m$?

Q. The 300N crate slides down the inclined curved path from A to B in the vertical plane as shown in the figure if the crate has a velocity of 1.2m/s down yhe inclined at point A and 8m/s at B. Find the work done against friction during the motion.

Q. A flexible chain of length l and mass m is slowly pulled at constant speed up over the edge of a table by a force F parallel to the edge of the table . Assuming that there is no friction between the table and chain , calculate the work done .

Q.

A boy pulls a toy with a force of 50 N through a string which makes an angle of 30° with the horizontal so as to move the toy by a distance of 1 m horizontally. If the string were inclined making an angle of 45° with the horizontal, how much pull would he apply along the string in order to move it the same distance of 1 m?

Q. 35.a man rides a cycle up the hill whose slope is 1 in 20.if the combined masses of man and cycle is 150kg and the man covers a distance of 100m along the incline.calculate the work done by the man .Neglect the effect of friction between tyres of cycle and land surface of hill.

Q.

A force of $5N$ moves the particle through a distance of $10m$. If $25joule$ of work is performed then the angle between the force and the direction of motion is

1. $0°$

2. $90°$

3. $30°$

4. $60°$

Q. Assertion : No work is done by a force on an object when the point of application of the force does not move.Reason : A small block of mass m is kept on a rough inclined surface of inclination a fixed in an elevator. The elevator goes up with a uniform velocity u and the block does not slide on the wedge.Then the work done by the force of friction on the block in time t will be mgutsin2a.(3) C(4) D

Q. Q.1) Mention some tasks which we do by engaging some animals. Q.2) Does a person going upstairs do any work? Q.3) How much work is done on a moving object when zero net force acts on it? Q.4) In which of the following cases, work is done? I) a crane picks up a fish and flies away 2) a boy tries to push a big rock 3) a body in uniform motion

Q. A particle of mass 2kg travelling in straight line with velocity v=\sqrt x where a is cons†an t.the work done by net force during displacement from x=0 to x=4m is?

Q.

A person A pushes a body of 5 kg placed on a rough surface of co-efficient of friction 0.3 by a distance of 4 m in 15 seconds. Another person B pushes the body of 7 kg on same surface by a distance of 3 m in the same time. Who has more energy and power?

1. A

2. B

3. Both A and B have developed equal power but B has more energy

4. Both A and B have developed equal power but A has more energy

Q. a body constrained to move along the z-axis under a cons†an t force \xrightarrow[F]{}=-i∧+2j∧+3k∧.work done by this force in moving the body a dis†an ce 4m along the z-a

Q.

A truck moves at a steady speed on a horizontal road. What is the work done by the road on the truck?

1. Negative work is done on the truck.

2. No work is done on the truck.

3. Not defined as the truck is non- living object.

4. Positive work is done on the truck.

Q. Kinetic friction can also do zero work.

1. True
2. False

Q.

A Man moves on a straight horizontal road with a block of 2kg in his hand. If he covers a distance of 20m with constant velocity of 1m/s. Find work done by man on block during motion.

1. 400J

2. 40J

3. zero

4. -10J

Q. Work done by frictional force depends upon path taken since it is a non conservative force, but still we use displacement while finding out the work done( by friction) . Why is it so?

Q.

A 1 kg block situated on a rough incline is connected to a spring of spring constant 100 N m^–1 as shown in Fig. 6.17. The block is released from rest with the spring in the unstretched position. The block moves 10 cm down the incline before coming to rest. Find the coefficient of friction between the block and the incline. Assume that the spring has a negligible mass and the pulley is frictionless.

Q.

A body moves a distance of 10 m along a straight line under the action of a force of 5 N. If the work done is 25 joule, the angle which the force makes with the direction of motion of the body is

1. $0^{\circ }$

2. ${30}^{\circ }$

3. ${60}^{\circ }$

4. ${90}^{\circ }$

Q. A uniform chain of length L and mass M overhangs a horizontal table with its two third part on the table. The friction coefficient between the table and the chain is $\mu$. Find the work done by friction during the period the chain slips off the table.