Question

The velocity of a car increase from 54km/hr to 72km/hr .How much is the work done if the mass of the car is 1500kg?

Answer 1

hey mate

⇒ Mass of car m =1500 kg

⇒ Initial velocity = 54 km/h

= 54 x 5/18

= 15 m/s

Final velocity = 72 km/h

= 72 x 5/18 = 20 m/s 

NOTE

(1 km/h = 1000 m/

(3600 s) = 5/18 m/s

Initial kinetic energy = ½ mv2

                              = ½ x 1500 x (15)2

                              = 168750 J

Increased kinetic energy = 1/2 mv2

                           = ½ x 1500 x (20)2

                           = 300000 J

Work done = Change in kinetic energy

                = 300000 - 168750

                = 131250 J

hence the work done by the force on the car = 131250 J

THANKYOU

Answer 2

as work done is equal.to change in kinetic energy..
and 72km/hr=20m/sec , 54km/hr=15m/sec
so,w =1/2 m(v2^2 - v1^2)
=>w=1/2 . 1500 (20^2-15^2)
=131250j
is the answer...