Page 76 - CITS - WCS - Mechanical

WORKSHOP SCIENCE - CITS

• Determine the horse power required to drive a lift in raising a load of 2000 kgf at a speed of 2 metre/sec, if the
efficiency is 70%.

Useful workdone to raise the lift in 1 sec
Force = 2000 kgf
Work = F x d

= 4000 w
Power output = 4000 w

Power input = Power output

Power input = 7.6 HP

• A mass of 100 gm is allowed to fall from a height of 10 metres. Determine the amount of Kinetic energy
gained by the body. (Take the value of g as 10 metre/ sec 2

Since initial velocity is 0 and distance travelled is 10 metres. final velocity 2
=V = 2 x g x s = 2 x 10x10 metre /sec 2
2
2
1 1
2
\ K.E = mv = × 100 gm × 200 metres 2 /sec 2
2 2
= 10000 gm metre 2 /sec 2
= 10 × 10 7 ergs

= 10 Joules.
K.E. developed by the vehicle at a constant speed
• A motor vehicle of one tonne is travelling at 60 km/hr. Calculate K.E of the vehicle at this speed.

K.E of the vehicle = mv 2
Where m = one tonne or 1000 kg
v = 60 km/hr
Solution
Changing v into meter/sec we get,

( 1km = 1000m)
( 1hour = 3600sec)

K.E.developed by a vehicle during acceleration
• A motor vehicle of 1200 Kg mass is being accelerated from 36 km to 48 km/hr speed. Calculate the increase
in K.E during its acceleration.

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CITS : WCS - Mechanical - Exercise 5 CITS : WCS - Mechanical - Exercise 5