## Tuesday, August 23, 2011

### Practice problems for class 9 SA1

Try to solve these problems, it will help you score good marks in Physics in first summative assessment.

1. Calculate the force required to be imparted to a car to give it a velocity of 30 m/s in 10 s. The mass of the car is 1500 kg.

2. For how long should a force of 200N act on a body of mass 2o kg so that it acquires a velocity of 100 m/s?

3. A force of 4 kg wt acts upon a body of mass 9.8 kg. Calculate the acceleration . Given g=9.8 m/s2

4. A 2000kg vehicle moving with a speed of 20 m/s is brought to rest in a distance of 50 cm. (i) find the acceleration (ii) Calculate the unbalanced force acting on the vehicle.

5. A motor car is moving with a velocity of 108 km/h and takes 4 s to stop after the brakes are applied. Calculate the force exerted by the brakes on the motor car if its mass along with passengers in the motor car is 1000 kg.

6. A bullet of mass 50 g is fired from a gun of mass 4 kg with an initial velocity of 35 m/s. Calculate the initial velocity of recoil of the gun.

7. A bullet of mass 20 g is fired horizontally from the pistol of mass 2 kg with a horizontal velocity of 150 m/s. What is the recoil velocity of the pistol?

8. Two persons with equal muscle power  manage to push a motor car of mass 1200 kg at a uniform velocity along a level road. The same motor car can be pushed by three persons with equal muscle power to produce an acceleration of 0.2 m/s. With what force does each person push the car?