Work

Q.

Calculate the work required to be done to stop a car of $1500\mathrm{kg}$ moving at a velocity of $60\mathrm{km}/\mathrm{h}$?

Q.

What is the relationship between joule and erg?

Q. A vertical spring with force constant k is fixed on a table.A ball of mass m at a height h above the free upper end of the spring falls vertically on the spring, so that the spring is compressed by a distance d.What is the net work done in the process?

Q.

Newton metre is the SI unit of:

1. Work
2. Power
3. Force
4. Acceleration

Q.

Joule is the SI unit of which of the following quantities?

1. Acceleration
2. Power
3. Work
4. Force

Q.

Distinguish between positive and negative work.

Q.

Is work a scalar or a vector quantity? How is it represented?

Q. Work done is measured as a product of force and displacement the direction of force.

1. along
2. opposite to
3. perpendicular to

Q. What is joule?

Q.

A 60 kg person climbs the stairs of height 20m in 10 minutes. Calculate the power delivered. Take $g=10m/s^2$.

1. 20 W

2. 10 W

3. 30 W

4. 60 W

Q.

State the mathematical expression of work

Q.

Look at the activity listed here. Reason out whether or not work is done in the light of your understanding of the term work.

Suma is swimming in a pond.

Q.

A centripetal force of 10 N is acting on a body in the circular motion of radius 1 m.
The work done by the force in one revolution is ___J.

Q.

Give one example of a machine for the use of changing the point of application of force.

Q.

The work done on an object lifted in the upward direction such that it moves at a constant speed, is:

1. F x displacement
2. (F + mg) x displacement
3. mg x displacement
4. 0

Q.

A body is moving in the direction opposite to the force acting on it. The work is done:

1. against the force

2. by the force or against the force depending on the amount of work

3. by the force

4. positive

Q.

What is the value of a vector dot a vector?

Q. Name the type of energy (kinetic or potential) possessed by a moving cricket ball.​

Q.

Which of the following factors does not influence the amount of work done?

1. Magnitude of displacement of the object

2. Direction of displacement of the object

3. Time taken to do the work

4. Force applied for executing the work

Q.

Work done upon a body is

1. a vector quantity

2. a scalar quantity

3. both (a) and (b)

4. none of these

Q. Question 1
Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term 'work'.
• Suma is swimming in a pond.
• A donkey is carrying a load on its back.
• A wind mill is lifting water from a well.
• A green plant is carrying out photosynthesis.
• An engine is pulling a train.
• Food grains are getting dried in the sun.
• A sailboat is moving due to wind energy.

Q.

Whenever a force causes displacement, work is said to be done.

1. True
2. False

Q.

What is the kinetic energy of a body of mass 10 kg moving at a speed of 10 m/s?

1. 1000 J

2. 1000 W

3. 500 W

4. 500 J

Q.

Choose the odd one out. Give reasons for your choice.

Inclined plane, lever, screw jack, watch, and pulley

Q.

Vijay is pulling a block with 22 N force and Gopal is pulling it with 10 N force in opposite direction. Vijay is able to pull the block a total distance of 6.5 m. Find the net work done by the two forces.

1. 85 J

2. 12 J

3. 78 J

4. 90 J

Q.

There are two mutually perpendicular forces acting on an object. One force acts in the direction of motion of the object and the direction of other force is perpendicular to the motion. During this interval, the kinetic energy of the body changes from 25 J to 100 J. The work done by the force acting perpendicular to the direction of the object is:

1. 75 J

2. 0 J

3. 100 J

4. 25 J

Q.

A loader applied 150 N of force to lift a stone and 1250 joules of work was done. How far was the rock lifted?

1. 9.3 m

2. 8.3 m

3. 5.3 m

4. 10.3 m

Q.

A man lifts a luggage of weight 100 N from the ground and puts it on his head 1.7 m above the ground. Calculate work done by him on the luggage.

1. 180 J

2. 200 J

3. 150 J

4. 170 J

Q.

Suman has been trying hard to push a wall but is unable to do so. Is he doing any work?

Q.

Hulk tried to move the wall of a fortress, but unfortunately, he was unable to do it. He applied a very large amount of force in the process.
Hence work done by Hulk is positive.

1. True

2. False