# Newton's laws of motion: questions and answers

1. A baseball is thrown at `150m//s^2` and its mass is `0.5kg`. What is the force?

`F=mxxa`

`F=0.5kgxx150m//s^2`

`F=75kgm//s^2`

Or

`F=75N` (Newtons)

2. Two skateboarders stand facing each other.

One skateboarder, the woman, weighing `57kg` pushes the other skateboarder the man who is `81kg` with a force of `85N`. What is the acceleration of each skater?

**Answer:**

Using Newton's third law, the force on the man must be equal and opposite to the womans, so it must be `85`Newtons. We could even say it is minus `85`Newtons.

Now using Newton's second law `F=ma`

Woman

`a=F/m`

`a=(85N)/(57kg)=1.49m//s^2`

Man

`a=F/m`

`a=(-85N)/(81kg)=-1.05m//s^2`