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
A mass of 10 kg is at a point A on a table. It is moved to a point B. If the line joining A and B is horizontal, what is the work done on the object by the gravitational force? Explain your answer.
State two factors on which the potential energy of a body at a certain height above the ground depends.
A body of mass m is moved from ground to a height h. If force of gravity on mass of 1 kg is g newton, find the work done in lifting the body.
Define the term potential energy of a body.
Is potential energy a vector or a scalar quantity?
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.
A weightlifter is lifting weights of mass 200 kg up to a height of 2 metres. If g = 9.8 m s−2, calculate :
work done by the weightlifter
On what factors does the gravitational potential energy of a body depend?
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?
A car is accelerated on a levelled road and acquires a velocity 4 times of its initial velocity. During this process, the potential energy of the car :
