Page 166 - WCS - Electrical

WORKSHOP CALCULATION & SCIENCE - CITS

4 A body of mass 5 kg is thrown up vertically with a velocity of 10 metres per second. Calculate the kinetic
energy of the body.
Solution: Mass of body m = 5 kg
Velocity v = 10 metres per second

Kinetic enerty of the body = ½ mv 2
= ½ x 5 x (10) 2
= 250 joules. Ans.
5 Find the Kinetic Energy of a body 3 kg moving with a velocity of 10 metres per second.
Solution: Mass m = 3 kg
Velocity v = 10 metres per second

Kinetic energy = ½ mv = ½ x 3 x(10) 2
2
= ½ x 3 x 100
= 150 joules.
6 What is the potential energy in a body mass 5 kg on top of a pole 20 metres high?

Solution: Mass m = 5 kg
Height h = 20 metres Potential energy = m.h. kg metres
= 5 x 20
= 100 kg metres
= 100 x 9.8 joules

[ 1 kg m = 9.8 joules]
= 980 joules
Potential energy = 100 kg metres or 980 joules
Assignments

1 The unit of energy in S.I. system is ………
a erg b calorie
c joule d kilowatt hour
2 The unit of power is ……..
a watt b erg
c joule d newton

3 A mass of 5 grams is moving with a constant velocity of 500 metres per second. Its Kinetic Energy is
………….
a 625 joules b 62.5 joules
b 6.25 joules d 6250 joules

4 The unit of power in M.K.S. system is …………
a dyne b joule
c watt d horse power
5 The unit of work in SI system is ………..
a 1 erg b joule

c foot poundal d kg-metre/sec

153

CITS : WCS - Electrical - Exercise 14