Newton's Laws of Motion

How does Newton's first law of motion explain the behavior of a skateboarder who comes to a stop after coasting on a flat surface?

• The skateboarder stops because an unbalanced force, such as friction, acts in the direction of motion.

• The skateboarder stops because an unbalanced force, such as friction, acts in the opposite direction of motion.

• The skateboarder stops because no forces are acting on them.

• The skateboarder stops because they are at rest and will remain at rest.

Answer explanation

According to Newton's first law, an object in motion stays in motion unless acted upon by an unbalanced force. In this case, friction acts in the opposite direction of the skateboarder's motion, causing them to stop.

If a 50 kg object and a 100 kg object are both pushed with the same force, which object will accelerate more and why?

• The 50 kg object will accelerate more because it has less mass.

• The 100 kg object will accelerate more because it has more mass.

• Both objects will accelerate equally because the same force is applied.

• Neither object will accelerate because mass does not affect acceleration.

Answer explanation

The 50 kg object will accelerate more because it has less mass. According to Newton's second law (F=ma), acceleration is inversely proportional to mass when the same force is applied.

A car and a truck are both moving at the same speed. If both vehicles apply their brakes with the same force, which vehicle will stop first and why?

• The car will stop first because it has less mass.

• The truck will stop first because it has more mass.

• Both will stop at the same time because the same force is applied.

• Neither will stop because mass does not affect stopping distance.

Answer explanation

The car will stop first because it has less mass. According to physics, when the same braking force is applied, a lighter vehicle experiences a greater deceleration, allowing it to stop more quickly than a heavier vehicle.

Explain how Newton's third law of motion is demonstrated when a person jumps off a small boat onto a dock.

• The boat moves towards the dock because the person pushes it.

• The boat moves away from the dock because the person pushes against it.

• The boat remains stationary because the forces cancel out.

• The boat moves in the same direction as the person jumps.

Answer explanation

When a person jumps off the boat, they exert a force against it, causing the boat to move away from the dock. This illustrates Newton's third law: for every action, there is an equal and opposite reaction.

A 10 kg object is subjected to a force of 20 N. According to Newton's second law, what is the acceleration of the object?

• 0.5 m/s²

• 2 m/s²

• 10 m/s²

• 20 m/s²

Answer explanation

According to Newton's second law, F = ma. Rearranging gives a = F/m. Here, F = 20 N and m = 10 kg. Thus, a = 20 N / 10 kg = 2 m/s². Therefore, the correct answer is 2 m/s².

How does friction play a role in the motion of a rolling ball coming to a stop?

• Friction acts in the direction of motion, causing the ball to speed up.

• Friction acts in the opposite direction of motion, causing the ball to slow down.

• Friction has no effect on the motion of the ball.

• Friction acts perpendicular to the direction of motion, causing the ball to change direction.

Answer explanation

Friction opposes the motion of the rolling ball, acting in the opposite direction. This force slows the ball down, ultimately bringing it to a stop, which is why the correct choice is that friction causes the ball to slow down.

If two ice skaters push off each other, how does Newton's third law explain their motion?

• Both skaters move in the same direction with equal speed.

• Both skaters move in opposite directions with equal speed.

• One skater moves while the other remains stationary.

• Both skaters remain stationary because the forces cancel out.

Answer explanation

According to Newton's third law, when the skaters push off each other, they exert equal and opposite forces. This results in both skaters moving in opposite directions, and due to their equal mass, they move with equal speed.

A force of 30 N is applied to a 5 kg object. What is the resulting acceleration according to Newton's second law?

• 5 m/s²

• 6 m/s²

• 30 m/s²

• 150 m/s²

Answer explanation

According to Newton's second law, F = ma. Here, F = 30 N and m = 5 kg. Rearranging gives a = F/m = 30 N / 5 kg = 6 m/s². Thus, the resulting acceleration is 6 m/s².

Describe the effect of mass on the acceleration of an object when a constant force is applied.

• Greater mass results in greater acceleration.

• Greater mass results in less acceleration.

• Mass has no effect on acceleration.

• Greater mass results in the same acceleration.

Answer explanation

According to Newton's second law, acceleration is inversely proportional to mass when a constant force is applied. Therefore, greater mass results in less acceleration.

How does Newton's first law of motion apply to a book resting on a table?

• The book will move on its own because it is at rest.

• The book will remain at rest unless acted upon by an unbalanced force.

• The book will move in the direction of the nearest force.

• The book will remain at rest because no forces are acting on it.

Answer explanation

According to Newton's first law, an object at rest will stay at rest unless acted upon by an unbalanced force. Therefore, the correct choice is that the book will remain at rest unless acted upon by an unbalanced force.