Question

What is the work to be done to increase the velocity of a car from 30 km h^-1 to 60 km h^-1if the mass of the car is 1500 kg?

Answer 1

Answer:

Explanation: to get answer in joules, every quantity should be in si units 60km/h=60*5/18 m/s

= 100/9 m/s

30km/h=50/9 m/s

ΔW=ΔKE=m(v²-u²)/2

= 1500 (10000-2500)/81*2

which is approx 69444 J = 69.444 KJ

Answer 2

Answer:

Work done is 156250 J.

Explanation:

Given,

The mass (m) of the car is 1500 kg.

Initial velocity of car = u = 30 km / hr = 30 * 5/18 = 25 / 3 m/s

Final velocity of car = v = 60 km / hr = 60 * 5/18 = 50/3 m/s

To find: The work to be done to increase the velocity of a car from

30 km h-1 to 60 km h^-1

Solution:

Initial kinetic energy = Ki = 1/2mu² = 1/2*1500*25/3 * 25/3 = 156250/3 J

Final Kinetic energy = Kf = 1/2mv² = 1/2*1500*50/3*50/3 = 625000/3 J

Work done can be given as change in Kinetic Energy,

i.e W = ΔK.E

or, W = Kf -  Ki

or, W = 625000/3 - 156250/3

or, W = 156250 J

Therefore, Work done is 156250 J.