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.

Male and female skaters standing 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

$a=F/m$

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