 # Energy

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• Q1

Define mechanical energy of an object.

Marks:1

Mechanical energy of the object is the sum of its kinetic and potential energy.

• Q2

What do you understand by the term energy?

Marks:1

Energy is the ability or capacity to do work.

• Q3

(a)Define kinetic energy. State some factors on which kinetic energy of body depends.
(b) State the kind of energy possessed by the following examples. Give reason to support your answer.
(i) A stone kept at the roof top.
(ii) An arrow shot from a bow.
(iii) A stone rolling down a hill.
(iv) A running car.
(v) A rubber sling of a catapult is stretched.

Marks:5

(a) The bodies in motion are capable of doing work and possess some energy. This energy is called kinetic energy. The kinetic energy of the body depends upon following factor:
i) The mass of the body i.e., more is the mass of a body, the more is its kinetic energy.
ii) The speed of the body i.e., more is the speed of a moving body, the more is its kinetic energy.

(b)(i) A stone kept at the roof top has potential energy due to its height. According to the relation:

Potential Energy = mgh

(ii) An arrow shot from a bow has kinetic energy due to its velocity. According to the relation: (iii) A stone rolling down a hill has kinetic energy due to its velocity. According to the relation: (iv) A running car has kinetic energy due to its speed. According to the relation: (v) When rubber sling of catapult is stretched, has potential energy due to change in the configuration or shape of the body.

• Q4

(a) What do you understand by term potential energy? (b) Mention two factors which determine potential energy.

(C) Give two examples of potential energy.

Marks:3

(a) The energy possessed by a body due to its position or configuration is known as the potential energy of the body.

(b)The two factors which determined potential energy of a body are:

1. Mass of the body,

2. Change in position of the body.

(c)Examples of potential energy:

1. We spend our muscular energy to wind up the spring of an alarm clock. This energy is stored in the spring as its potential energy due to its configuration.

2. When the string of bow is pull, the muscular energy is stored in the string and bow in the form of potential energy. It is the potential energy which makes the arrow shoot out.