English Medium इयत्ता ९ - CBSE Question Bank Solutions for Science

Which of the following could not be a unit of acceleration?

A bus increases its speed from 36 km/h to 72 km/h in 10 seconds. Its acceleration is :

The slope of a speed-time graph gives:

Two bodies A and B of equal masses are kept at heights of h and 2h respectively. What will be the ratio of their potential energies?

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 :
potential energy acquired by the weights.

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

A boy weighing 50 kg climbs up a vertical height of 100 m. Calculate the amount of work done by him. How much potential energy does he gain? (g = 9.8 m/s²)

To what height should a box of mass 150 kg be lifted, so that its potential energy may become 7350 joules? (g = 9.8 m/s²)

On what factors does the gravitational potential energy of a body depend?

Give one example each of a body possessing : (i) kinetic energy, and (ii) potential energy.

A body of mass 2 kg is thrown vertically upwards with an initial velocity of 20 m/s. What will be its potential energy at the end of 2 s? (Assume g = 10 m/s²).

Explain by an example what is meant by potential energy. Write down the expression for gravitational potential energy of a body of mass m placed at a height h above the surface of the earth.

What is the difference between gravitational potential energy and elastic potential energy? Give one example of a body having gravitational potential energy and another having elastic potential energy.

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)

When a ball is thrown vertically upwards, its velocity goes on decreasing. What happens to its potential energy as its velocity becomes zero?

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,

1. how much work does man do against gravity?
2. 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 :