18. Exercises XVIII

1. Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her? Why?

 

 

The acceleration of an object can be zerocannot be zero even if several forces are acting on it provided the resultant force (F) is zeropositivenegative (because mass ‘m’ cannot be zerocan be zero).

 

2. A freely falling object eventually stops on reaching the ground. What happens to its kinetic energy?

 

When an object falls freely towards the ground, its potential energy remains the samedecreasesincreases, and kinetic energy increasesremains the samedecreases; as the object touches the ground, all its kinetic energy becomes potential energypotential energy becomes zeropotential energy becomes kinetic energykinetic energy becomes zero.

 

Since the object hits the laborious ground, all its kinetic energy becomes heat energy and sound energykinetic energy becomes potential energykinetic energy becomes zeropotential energy becomes zero. It can also deform the ground depending upon the ground’s nature and the amount of kinetic energy possessed by the object.