Examples of Work Done

Q.

The work done in slowly lifting a body from earths surface to a height R (radius of earth) is equal to two times the work done in lifting the same body from earths surface to a height h. Here h is equal to

1. 

2. 

3. 

4. 

Q.

A body of mass m is moving in a circle of radius r with a constant speed v. The force on the body is $\frac{m{v}^2}{r}$ and is directed towards the centre. What is the work done by this force in moving the body over half the circumference of the circle

1. $\frac{m{v}^2}{r}\times \pi r$

2. $Zero$

3. $\frac{m{v}^2}{r^2}$

4. $\frac{\pi r^2}{m{v}^2}$

Q. The work done to raise a mass $m$ from the surface of the earth to a height $h$, which is equal to the radius of the earth is

1. $mgR$
2. $2mgR$
3. $\frac{1}{2}mgR$
4. $\frac{3}{2}mgR$

Q.

A body of mass 100 g is rotating in a circular path of radius r with constant velocity. The work done in one complete revolution is

1. $100rJ$

2. $\left(\frac{r}{100}\right)J$

3. $\left(\frac{100}{r}\right)J$

4. Zero