Question

Two toy-cars A and Bof masses 200 g and 500 g respectively are moving with the same speed. Which of the two has greater kinetic energy?

Answer 1

CAR A                                            CAR B 

mas= 200g                                    mass = 500 g 

=`200/1000`=`1/5` kg                     =`500/1000`=0.5 kg 

       =0.2kg 

K.E.=`1/2` M`V^2`               ∴  speed of both cars
                                             is same 

K.E. =`1/2`× 0.2 ×`V^2`       K.E. of B=`1/2` ×0.5× `V^2`

=0.1 `v^2`                                      =0.25 `v^2`

0.25 `v^2` is greater than 0.1`v2`

∴ K.E. of car B is greater.
Or
Since speed of both cars is same
∴ The speed of car having greater mass (i.e. of car B), the K.E. is greater
∴  Kinetic energy of car B having greater mass is greater.