Question

1. explain how each of newtons three laws of motion applies to riding a skateboard.
2. a car moving at constant velocity suddenly brakes to a stop. explain what happens to the passengers in terms of inertia.
3. imagine pushing a box across the floor. describe all the forces acting on the box and identify which are balanced and which cause motion.

Explanation:

Question 28:

Newton's first law (law of inertia): A skate - boarder at rest stays at rest and a moving skate - boarder keeps moving in a straight line unless acted on by an external force like friction or pushing off the ground. Newton's second law ($F = ma$): When a skate - boarder pushes off the ground with a force, the acceleration of the skate - boarder depends on their mass and the force applied. Newton's third law: When the skate - boarder pushes down on the ground, the ground pushes back up on the skate - boarder with an equal and opposite force, allowing them to move.

Question 29:

The passengers in the car have inertia. When the car is moving at a constant velocity, the passengers are also moving at that velocity. When the car brakes suddenly, the car stops due to the braking force, but the passengers' bodies tend to continue moving forward at the original velocity because of inertia.

Question 30:

Forces acting on the box include the gravitational force ($F_g$) pulling it downwards and the normal force ($F_N$) from the floor pushing it upwards. These two forces are balanced. The applied force ($F_{app}$) by the person pushing the box and the frictional force ($F_f$) opposing the motion are unbalanced. The applied force causes the box to move if it is greater than the frictional force.

Answer:

Question 28:

Newton's first law: A skate - boarder's state of motion changes only with an external force. Second law: Pushing off the ground gives an acceleration based on mass and force. Third law: Ground reaction force enables movement.

Question 29:

Passengers' bodies continue moving forward due to inertia when the car stops.

Question 30:

Balanced: Gravitational and normal forces. Unbalanced: Applied and frictional forces; applied force causes motion if it exceeds friction.