Question

Rashmi was playing on a swing in a park. To increase her speed when her swing was at its lowest position during its oscillations she pushed the ground hard with her feet. She enjoyed it but could not understand the mechanism. Her elder brother Pankaj explained to her the reason. when she asked him.
i.What type of energy was possessed by Rashmi while swinging? On what factors does it depend?
ii.Why did the swing's speed increase on pushing the ground harder with feet?
iii.Why and what did Rashmi ask Pankaj?

Answer 1

Hint: With the help of the law of conservation of energy we can answer the first part. Using newton’s second law of motion we can answer the second part. As it is given that she was not able to understand the mechanism keeping her situation in mind we will answer the third part of the question.

Complete answer:
Potential energy, which is stored energy, and kinetic energy, which is the energy of motion, are both present while swinging. The mechanical energy of the system is made up of them. As a person swings, their potential energy transforms into kinetic energy, then back to potential energy, and so on. All of the swing's mechanical energy is potential energy at the highest points as kinetic energy becomes zero. While going upwards or coming downwards the potential energy changes to kinetic energy and the swing keeps on moving. This conversion of energy continues unless an external force stops it.

According to newton’s second law force applied to the body is directly proportional to the acceleration of that body. So, by pushing the ground by feet a force is applied. Hence, the swing's speed increases on pushing the ground harder with feet.
Rashmi inquired of her brother Pankaj as to why the pace of the swing rises when she pushes the ground with her feet. She inquired because she was interested as to why the speed of the oscillations increased when she pushed the ground to its lowest level.

Note:
Friction from the air molecules resists the swing's movement as it passes through the air. This converts some of the kinetic energy of the swing into thermal energy, which is then released into the environment. If no force is applied while swinging the swing slows down as the kinetic energy decreases. The swing comes to a halt when all of its mechanical energy has been converted to heat energy.