Use the formula below for this question:

re-arrange to solve for a:

now simply plug in your variables and there's your answer :). If you ever get stuck, you can look up the kinematic equations!
Answer:
Explanation:
Given

Frictional Force is balanced by force due to car acceleration
Frictional force 




Structural constraint is the answer :)
Answer:
Both balls have the same speed.
Explanation:
Janelle throws the two balls from the same height, with the same speed. Both balls will have the same potential and kinetic energy. Energy must be conserved. When the balls pass Michael, again they must have the same potential and kinetic energy.
'Pressure' is (force) / (area).
The only choice with those units is #1 .