ch5 Newton's Third Law of Motion

These flashcards cover key concepts from Newton's Third Law of Motion, including forces, action-reaction pairs, and applications in various physical scenarios.

What does Newton's Third Law of Motion state?

Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.

What are action and reaction forces?

Action and reaction forces are co-pairs of a single interaction; one is the action force and the other is the reaction force.

Give an example of Newton's Third Law in action.

When a soccer player kicks a ball, the player exerts a force on the ball and the ball exerts an equal and opposite force on the player's foot.

In which direction do action and reaction forces act?

Action and reaction forces act in opposite directions.

Do action and reaction forces act on the same object or different objects?

They always act on different objects.

What is the force experienced by a soccer player when they kick a ball with 1500 N of force?

The ball exerts a reaction force of 1500 N against the player's foot.

What happens when a person steps off a curb?

The Earth pulls the person downward while the person pulls the Earth upward.

Why doesn’t the person feel Earth moving upward when they step off a curb?

The Earth moves by an imperceptible amount due to its enormous mass.

Explain why the accelerations of a cannon and cannonball are different when fired.

They have different masses; the same force results in different accelerations according to Newton's second law.

How does mass affect acceleration in Newton's Third Law?

A small mass will experience a large acceleration when the same force is applied as compared to a large mass.

What happens during a collision between a bus and a bug in terms of forces?

Both the bus and the bug experience equal and opposite forces, but the effects are very different due to their masses.

What occurs when two equal mass people push off each other on slippery ice?

Both will move at the same speed in opposite directions due to equal forces.

How does an external force affect the acceleration of an object?

An external force can cause the object to accelerate according to Newton's second law.

What is the goal of identifying action and reaction forces?

To understand the interaction between objects and how forces balance out.

In the apple and orange system, what type of forces are action and reaction?

The action by one fruit on the other does not cancel out as they act on different objects.

What is an essential condition for a system to accelerate?

It needs an external force acting on it; otherwise, internal forces will cancel out.

Describe how a bird flies using Newton's Third Law.

A bird pushes air downward, which causes the air to push it upward, allowing it to fly.

What determines the lift generated by an airplane wing?

The wing deflects air downward, creating an upward lift force due to Newton's Third Law.

How does a heavier glider maintain altitude compared to a lightweight glider?

A heavier glider must push down the air with greater force to equal its weight.

What is the force pair when you pull on a sled?

The force exerted on the sled by you is matched by the sled's reaction force on you.

Which forces act on an object on an inclined plane?

The weight force acting downward and the normal force acting perpendicular to the surface.

What remains constant as the angle of a ramp increases?

The weight of the object (mg) remains constant.

What happens to the normal force as the incline increases?

The normal force (N) decreases with an increased angle of the ramp.

What is the net force on a block when a ramp is vertical?

The net force on the block is its weight (mg) when the ramp is vertical.

What creates a friction force on the ceiling when pulling an object in an upward motion?

A normal force acts on the object, opposing the gravitational force.

What effect does air resistance have on a falling object?

Air resistance opposes the motion of the object, affecting its acceleration.

Explain the concept of vector components in physics.

Vector components are the vertical and horizontal aspects of a vector; they are perpendicular to each other.

When resolving forces, what determines the greater component?

The larger component is determined by the direction and magnitude of the force applied.

What are two forces acting on a block of ice being pushed up a ramp?

Weight (mg) acting downward and a normal force (N) acting perpendicular to the surface.

How does a helicopter achieve lift when the lift force exceeds its weight?

The helicopter moves upward when lift is greater than its weight.

What is the difference in acceleration for objects with different masses under the same force?

A smaller mass will accelerate more than a larger mass under the same force.

In the apple-orange system, how does friction play a role?

Friction from the floor must counterbalance the action forces between the fruits for designated acceleration.

What does Newton's Second Law describe?

Net force acting on an object leads to acceleration, which is directly proportional to the force and inversely proportional to mass.

What happens to action and reaction forces within a closed system?

They do not produce a net force leading to acceleration; they cancel each other out.

What principle allows a bird to fly?

A bird pushes air downward, which in turn pushes it upward due to an action-reaction force pair.

What must be true for a bird to maintain flight?

The lift force must equal the weight force acting on the bird.

How can the direction of a vector influence the components of a force?

The angle of the vector determines how much force is directed in horizontal versus vertical components.

Why don't you feel the Earth moving when you jump?

Because the Earth’s mass is so large that any motion resulting from the reaction force is imperceptible.

What is an action force when a rocket launches?

The rocket engines expel gas backward, which is the action force.

What is the reaction force when a rocket launches?

The expulsion of gas creates an equal and opposite force that pushes the rocket upward.

What happens to forces when two objects collide?

Both experience equal forces, producing different effects due to their differing masses.

What is the significance of a normal force?

It acts perpendicular to surfaces preventing objects from passing through each other.

In a tug-of-war scenario, what ensures the forces are equal?

Both teams exert equal and opposite forces on the rope, keeping it stationary if no one is winning.

When do action and reaction forces not cancel?

They do not cancel when they act on different objects.

What dictates whether objects accelerate or not?

The net external force acting on the objects determines whether they accelerate.

How do slight wings in airplane design contribute to flight?

They generate lift by deflecting air downward, creating an upward force on the wings.

What defines inertia according to Newton's First Law?

An object at rest tends to remain at rest; an object in motion tends to remain in motion at constant speed.