Advertisements
Advertisements
Question
If 784 J of work was done in lifting a 20 kg mass, calculate the height through which it was lifted. (g = 9.8 m/s2)
Advertisements
Solution
Mass of the box (m) = 20 kg
Acceleration due to gravity (g) = 9.8 m/s2
Work done against gravity (W) = 784 J
Let the height above the ground be (h)
So, W = m × g × h
So, height can be calculated as,
`h = W/(m xx g)`
So ,
`h = 784/(20 xx 9.8) m`
= `784/196 m`
= 4 m
So the body is lifted to a height of 4 m.
APPEARS IN
RELATED QUESTIONS
State two factors on which the potential energy of a body at a certain height above the ground depends.
Write the expression for the gravitational potential energy explaining the meaning of the symbols used.
The gravitational potential energy stored in a box of weight 150 kgf is 1.5 × 104 J. Find the height of the box. Take 1 kgf = 10 N.
Define the term potential energy of a body.
A spring is kept compressed by a small trolley of mass 0.5 kg lying on a smooth horizontal surface as shown in the adjacent fig. When the trolley is released, it is found to move at a speed v = 2 m s-1. What potential energy did the spring possess when compressed?
State whether the following statement is true or false :
The potential energy of a body of mass 1 kg kept at a height of 1 m is 1 J.
What happens to the potential energy of a body when its height is doubled?
Give one example each of a body possessing : (i) kinetic energy, and (ii) potential energy.
A man is instructed to carry a package from the base camp at B to summit A of a hill at a height of 1200 metres. The man weighs 800 N and the package weighs 200 N. If g = 10 m/s2,
- how much work does man do against gravity?
- what is the potential energy of the package at A if its is assumed to be zero at B?
The potential energy is
