Question

Two motor cars are moving with velocities of 18km/h and 54 km/h on a highway. Find the ratio of their kinetic energies if mass of the cars is 200kg and 400 kg respectively?

Answer 1

Answer:

Initial Velocity, u=54km/hr=15m/s

Final velocity , v=72km/hr=20m/s

Mass =1500kg

Initial kinetic energy

2

1

mu

2

⇒

2

1

1500×15×15=168750J

Final kinetic energy

2

1

mv

2

⇒

2

1

1500×20×20=300000J

So, change in kinetic energy = work done=300000−168750=131250J

Answer 2

Answer:

1:18

Explanation:

kinetic energy=

$1 \2 {mv}^{2}$

for 1st kinetic energy= 1/2×200×18×18

for 2nd= 1/2×400×54×54

when both will be taken in ratio 162:2916 when we solve it ans will come 1:18