Question

a car and truck have the same speed of 30m per second if their mass are in the ratio 1:3 find the ratio of their kinetic energy

Answer 1

let the mass of car is x
and mass of truck is 3x

then kinetic energy of car=1/2×x×30×30
and truck =1/2×3x×30×30
so (k.e of car)/(k.e of truck)=1:3

Answer 2

Given that velocity of the car = 30m/s.

Given that velocity of the truck = 30m/s.

the velocity of the car = velocity of the truck.

We know that kinetic energy = 1/2mv^2.

Given that Their mass is in the ratio = 1:3.

Kinetic energy of car = 1/2 * 1 * (30)^2

                                    = 450.


Kinetic energy of truck = 1/2 * 3 * (30)^2

                                       = 1350.


Therefore the ratio of kinetic energy = 450/1350

                                                              = 1/3

 
Therefore the ratio = 1:3.


Hope this helps