How would you answer this?

Question

A 2-kg body of mass is moving on a horizontal frictionless surface with a velocity of 4 m/s. What is the net force required to keep the body moving with the same velocity and direction for 5 s?

I believe you would just use f=ma => f-(2)(4) => f=8n

But I just want to make sure.

Thanks in advance

Answer 1

You need to pay attention to units. 4 m/s is a velocity. The law of inertia says that objects maintain their velocity unless acted upon by an external net force. Therefore, the force is 0 horizontally in this case. Using the second law, the unchanging velocity implies an acceleration = 0 and, therefore, F_Net = 0