Question

A body with a mass of 5 Kg has the same kinetic energy as a second body. The second body has a mass of 10 kg and is moving at a speed of 20 m/s. How fast is the second body moving?

Answer 1

First body:


`E_(k_1)=(1)/(2).m.v^2\\ \\ E_(k_1)=(1)/(2).5.v_1^2=(5)/(2).v_1^2`

Second body:


`E_(k_2)=(1)/(2).m.v_2^2\\ \\ E_(k_2)=(1)/(2).10.(20)^2=2.000 \ J`

From description of the task we have:


`E_(k_1)=E_(k_2)\\ \\ (5)/(2).v_1^2=2.000 \ J\\ \\ 5.v_1^2=4.000 \ J\\ \\ v_(1)^2=800 \ J\\ \\ v_(1)= √(800) \ J \approx 28,3 \ m/s`