Work Energy Theorem

Q.

A child is moving on a skateboard with a speed of $2m{s}^{-1}$. After a force acts on him, his speed becomes $3m{s}^{-1}$. Calculate the work done by the force, if the mass of the child is $20kg$.

1. 100 J

2. 20 J
3. 50 J
4. 320 J

Q.

What is the amount of work to be done on a car of mass $\text{1000 kg}$ to increase its velocity from $10kmh{r}^{-1}$ to $20kmh{r}^{-1}$?

1. $\text{12596 J}$

2. $\text{10590 J}$

3. $\text{11592 J}$

4. $\text{13542 J}$

Q. A force causes a stationary body of mass $12kg$ to be accelerated at a rate of $2m{s}^{-2}$ . If the final velocity of the body is $8m{s}^{-1}$, find the work done by the force.

1. $360J$
2. $384J$
3. $396J$
4. $420J$

Q.

A car of mass $2000kg$ travelling with a uniform velocity of$2m{s}^{-1}$accelerates till its velocity becomes $22m{s}^{-1}$. The work done on the car is

1. $4.8KJ$

2. $480KJ$

3. $48KJ$

4. $500KJ$

Q. Force exerted by spring is

1. none of these
2. gravitational force
3. electrostatic force
4. restoring force