Some physics problems..explanations needed?

Question

1. When a car stops suddenly, what causes the passengers to be thrown forward out of their seats (if they're not wearing a seatbelt)? are they really thrown forward?

2.why do the safety nets that circus performers use provide a safer landing than if they had just landed on the ground?

3.If you hit the sidewalk with a hammer, the hammer bounces back at you. How does this process involve Newton's third law?

4.if u're driving in a dense fog and can't see the meters on your dashboard or anything outside the car, a)how can you tell if your car is speeding up or slowing down b) Can you tell if your car is at rest or is moving with uniform velocity?

5. if u're in a spaceship and you notice that if you release an object, it accelerates toward your feet at 9.8 m/s^2. a) what can you conclude about the motion of the spaceship? b) what force do you feel on your feet from the floor c) explain how your observations lead you to believe that gravity is present d)Is gravity really present ?

Answer 1

1- it is the momentum that they have while the car was moving. when the car stops they still have the momentum for a while.

2- safety net makes the stopping time longer so they dont get damaged because of force on their body. force is much lesser with safety net.

3- sidewalk is very big size according to hummer. so momentum is same before the impact and after the impact.

4- you can fell the force of acceleration it is the 2nd law. F=ma

5- motion of space ship is accelaration with a 9.8m/s^2

force is equal to gravity on your feet

gravity is present because all abjects tent to go down

yes