Page 87 - Physics - XI

Sources of Error

1. The inclined planes may not be frictionless.
2. The planes may be shaky.

VIVA VOCE

Q1. Defi ne kinetic energy and give its expression.
Ans. The energy possessed by a body by virtue of its motion is called its kinetic energy. If a body of mass
m is moving with the velocity v, its kinetic energy will be given as:

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Kinetic energy = mv 2
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Q2. Defi ne potential energy and give its expression.
Ans. The energy possessed by a body due to its position or confi guration is called potential energy.
Expression for the potential energy is given as

Potential energy = mgh
where m is the mass of the body, h is the height from the earth's surface.
Q3. What is energy?
Ans. The capacity of doing work is called energy.

Q4. Give the SI unit of energy.
Ans. J (joule)

Q5. State various forms of energy.
Ans. Various forms of energy are: mechanical energy, thermal energy, light energy, sound energy, magnetic
energy, chemical energy, electrical energy, nuclear energy, etc.

Q6. Defi ne law of conservation of energy.
Ans. It states that the sum of all forms of energy in the universe remains constant. Energy can neither be
created nor destroyed, but it can be changed from one form to another.

Q7. Can this activity be performed successfully with a steel ball of smaller diameter? (NCERT)
Ans. Yes
Q8. If the ball is not reaching exactly upto the same height on the other wing, comment on the
observations. NCERT)
Ans. The ball does not reach exactly up to the same height on the other wing due to the air friction.

ACTIVITY - 7

Aim
To study dissipation of energy of a simple pendulum by plotting a graph between square of amplitude and
time.

Apparatus and Materials Required
A pendulum bob, a split cork, thread, metre scale, a clamp stand, stopwatch, and a chalk piece

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