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 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?
(i) At the extreme position of the swing she will have potential energy. At the mean position of the swing, she will have kinetic energy. These energies keep interchanging during the motion of the swing.
The kinetic energy depends on the velocity of the mass so it will be greatest at the bottom and, zero at the top. The gravitational potential energy depends on the height. It will be maximum at the top of the swing and minimum at the bottom.
(ii) On pushing ground harder with the feet, force is applied on the swing. As a result of it the swing starts moving with the greater speed and the speed of the swing increases.
(iii) Rashmi asked her brother pankaj that why on pushing the ground with the feet the speed of the swing increases. She asked so because she is curious to know that why the speed of the oscillations was increasing on pushing the ground when at the lowest position.
Rate this question :
Name the devices or machines which convert:
(i) Electrical energy into sound energy.
(ii) Hear energy into kinetic energy (or mechanical energy).
(iii) Chemical energy into kinetic energy (or mechanical energy).
(iv) Chemical energy into heat energy.
(v) Light energy into heat energy.Lakhmir Singh & Manjit Kaur - Physics
Which one of the following is not the unit of energy?
A. Joule B. Newton-metre
C. Kilowatt D. Kilowatt-hourLakhmir Singh & Manjit Kaur - Physics
Explain the transformation of energy in the following cases:
(i) A ball thrown upwards.
(ii) A stone dropped from the roof of a building.Lakhmir Singh & Manjit Kaur - Physics
Name the quantity whose unit is:
(b) Kilowatt – hourLakhmir Singh & Manjit Kaur - Physics
Define the term ‘energy’ of a body. What is the SI unit of energy?Lakhmir Singh & Manjit Kaur - Physics