Understanding Newton's First & Third Laws

Which of the following is an example of inertia in daily life?

• A car accelerating when the driver presses the gas pedal

• A book remaining at rest on a table until someone moves it

• A ball rolling down a hill

• A bird flying in the sky

Answer explanation

Inertia is the tendency of an object to remain at rest or in motion unless acted upon by an external force. A book on a table stays at rest until someone moves it, illustrating inertia effectively.

How does Newton's first law of motion apply when you are riding a bus and it suddenly stops?

• You remain in your seat without moving

• You move forward in your seat

• You move backward in your seat

• You stay at rest

Answer explanation

According to Newton's first law, an object in motion stays in motion. When the bus stops suddenly, your body tends to continue moving forward due to inertia, causing you to move forward in your seat.

Which scenario best illustrates the concept of inertia?

• A soccer ball being kicked and changing direction

• A train continuing to move at a constant speed on a straight track

• A car turning a corner

• A person jumping off a diving board

Answer explanation

Inertia is the tendency of an object to resist changes in its state of motion. A train moving at a constant speed on a straight track exemplifies this, as it continues moving without external forces acting on it.

Consider a scenario where a book is placed on a table. What will happen to the book if no external force acts on it?

• It will start moving

• It will remain at rest

• It will fall off the table

• It will rotate

Answer explanation

According to Newton's first law, an object at rest will remain at rest unless acted upon by an external force. Since no external force is acting on the book, it will remain at rest on the table.

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Why is it important to wear seatbelts in a car, according to Newton's first law of motion?

• To prevent the car from moving

• To keep passengers from moving forward in case of a sudden stop

• To increase the speed of the car

• To make the car more comfortable

Answer explanation

According to Newton's first law, an object in motion stays in motion. Wearing seatbelts keeps passengers from moving forward during a sudden stop, preventing injury by counteracting their inertia.

A hockey puck slides on ice at a constant speed. What can be inferred about the forces acting on it?

• There is a net force acting on the puck

• The forces are balanced

• The puck is accelerating

• The puck is decelerating

Answer explanation

Since the hockey puck slides at a constant speed, it indicates that the forces acting on it are balanced. If there were a net force, the puck would either accelerate or decelerate, which is not the case here.

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A magician pulls a tablecloth out from under a set of dishes without moving them. Which principle does this demonstrate?

• Action and reaction

• Inertia

• Acceleration

• Gravity

Answer explanation

The magician's action demonstrates inertia, which is the tendency of an object to remain at rest. The dishes stay in place because they resist changes to their motion, allowing the tablecloth to be pulled out smoothly.

In a real-world scenario, why does a rolling ball eventually come to a stop?

• Because of inertia

• Due to an unbalanced force like friction

• Because it loses mass

• Due to gravity pulling it down

Answer explanation

A rolling ball comes to a stop due to an unbalanced force like friction acting against its motion. Inertia keeps it moving, but friction gradually slows it down until it stops.

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What would happen to a spacecraft in space if its engines were turned off?

• It would stop immediately

• It would continue moving at the same speed and direction

• It would accelerate

• It would fall back to Earth

Answer explanation

In space, if a spacecraft's engines are turned off, it will continue moving at the same speed and direction due to inertia, as there is no air resistance or external forces to stop it.

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When you push against a wall, why don't you move the wall?

• The wall is fixed to the ground

• The wall exerts an equal and opposite force back on you

• The wall is too heavy

• Your force is not strong enough

Answer explanation

When you push against a wall, it exerts an equal and opposite force back on you, as described by Newton's third law of motion. This reaction force prevents you from moving the wall.

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