Easy physics word problems

1. Newton's first law predicts that objects will continue their motion at constant speed when no forces are acting on them. In reality, this does not happen. When you stop pushing a cart, the cart eventually slows and stops. Explain how Newton's first law can be true even though it disagrees with the observation that a pushed cart stops when you remove your pushing force.

2. Give an example of a situation where the speed and acceleration are in opposite directions. Your answer should identify the force associated with the acceleration.

3. When you push on a door, it opens. The force you exert generates an equal and opposite reaction force. Why don't the two forces cancel out, leaving zero net force (and not moving the door)?

4. When you walk, you push against the ground with your feet. What pushes you and allows you to move forward? Use Newton's third law to explain walking.

1) the cart slows down because there ARE forces acting on it, like the friction of the ground and gravity is always acting on the cart.

2) driving a car say east bound and you step on the brake. You're speed or velocity is east but the force from the brake is west

3) when you first move the door you put a force larger than the force of the door (if only for a split second) after the door is moving the net forces are equal

4) the ground pushes you