Question

If a car of mass 1200 kg has a speed of 5 m/s, how much kinetic energy would it need to gain in order to speed up to 15 m/s? (Number only; write out the full number)l

Answer 1

K.E in 1st case : 1/2 m v²

=15000J

K.E needed : 1/2 m v²

=135000J

Thus, K.E to be gained = 135000-15000

=120000J

Answer 2

k.e=1/mv^2

k.e for for speed of 5m/s

=1/2(1200)(25)

=1/2(30000)

=15,000

k.e for speed of 15m/s

=1/2(1200)(225)

=1/2(270000)

=1,35,000

required k.e is

=1,35,000-15,000

1,20,000