Question

Please help! A net force of 2.0 N acts on a 2.0-kg object for 10 seconds. What is the object’s kinetic energy after that 10 seconds (assuming the object starts from rest and there is no friction)?

Answer 1

For Newton's second law, the force F applied to the object of mass m will cause an acceleration a of the body:

`F=ma`
So, the acceleration is

`a= (F)/(m)= (2.0 N)/(2.0 kg)=1 m/s^2`

The object undergoes through this acceleration for 10 seconds, t=10 s. Since it is an accelerated motion, we can find its final velocity after 10 seconds:

`v_f = v_i + at=0 m/s+(1m/s^2)(10 s)=10 m/s`
where
`v_i` is the initial velocity of the object, which is zero since it starts from rest.

Finally we can calculate the final kinetic energy of the object, which is given by

`K= (1)/(2)mv^2= (1)/(2)(2.0 kg)(10 m/s)^2=100 J`