Question

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

Answer 1

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 
(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 = 131250J 

Answer 2

Answer:

131250J

Explanation:

initial kinetic energy =54km/hr*5/18m=15m/s

final kinetic energy=72km/hr *5/18=20m/s

kinetic energy =1/2mv2

=1/2*1500*(15)2

=168750J

final kinetic energy