Newton's Third Law of Motion (Action and Reaction)

Last updated 3 months ago

30 Nsɛmmisa

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Laabri

Newton's Third Law of Motion (Action and Reaction)

Last updated 3 months ago

30 Nsɛmmisa

Try to imagine two colliding objects (like two cars or a bat and a ball) as a system.

Think about what forces or energy are going into the system and out of the system.

What impact do those forces have on the system as a whole?

Scientists and engineers are always looking for ways to reduce the damage that might be caused when two objects collide.

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Why would scientists study collisions in sports?

To force players to quit.

To reduce injury and improve performance.

To make games last longer.

To add more players to teams.

Whenever you apply a force to an object, it applies the same force back on you. These forces are equal and act in opposite directions. This is Newton’s Third Law, which states that every action has an equal and opposite reaction.

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However, just because the forces are equal and opposite, this does not mean that they have the same effect.

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What does Newton's Third Law state?

Forces can be combined to strengthen them.

Every action has an equal and opposite reaction.

Action forces are stronger than reaction forces.

Equal forces always have the same effect.

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When you kick a soccer ball, you apply a force to the ball, and it pushes back on you with the same force.

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If the forces are equal, why does the soccer ball move and you don’t?

You have a lot more mass than the soccer ball. Remember that the more mass an object has, the more force is needed to move it, so the soccer ball takes less force to move than you do.

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The force acting on the soccer ball is big enough to make the ball move. The opposite force acting on you is not big enough to make you move because you have more mass and, therefore, more intertia.

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Let’s take a look at another example. You witness a head-on collision between a large semi-truck and a small sports car. Both were driving the speed limit, approximately 25 miles per hour.

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You notice the semi-truck appears to have sustained very little damage while the sports car appears truly beat up.

If they were going the same speed and we know that Mr. Newton claims forces are equal and opposite, then why didn’t both cars have the same amount of damage?

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Why did the semi-truck sustain less damage than the sports car?

The sports car was old and weak.

They collided at different speeds.

It has more mass and structural strength.

The truck driver braked suddenly.

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It has to do with momentum. Momentum is how hard it is to stop a moving object and depends on the object’s mass and acceleration.

More force = more momentum = harder to stop.

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In our crash example, the acceleration of both cars is the same, however like the soccer ball example, the semi-truck has a higher momentum than the sports car because the semi-truck has a higher mass.

This creates a difference in momentum, and even though the forces were equal and opposite in direction, the sports car had a smaller momentum and took more damage.

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Continuing with the car crash example, what prevents the small sports car from being pushed back too far?

There are some outside and unseen forces that prevent objects from transferring too much momentum.

Gravity pulls objects towards the center of Earth. As it does so it causes the objects to be in contact with the ground. This force pulling down creates frictional forces with the object and the road surface resisting movement and significantly decreasing the object’s momentum.

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Another example is when you release the air out of a balloon. If you let go of a balloon without tying it closed, the air rushes out of the balloon and the balloon goes flying in the other direction.

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Another example of Newton’s third law involves normal force. A normal force is the support force exerted on an object that is in contact with another stable object.

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The most common normal force is a reaction to gravity. Gravity is pulling you down toward the ground. In this case, the normal force is from the ground pushing up against your feet.

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Sometimes when people go rifle shooting and use a scope on their gun, they end up with the type of injury shown below.

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Create a model that shows the forces involved when a person shoots a gun and design a solution to help protect them.

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Try to imagine two colliding objects (like two cars or a bat and a ball) as a system.

Think about what forces or energy are going into the system and out of the system.

What impact do those forces have on the system as a whole?

Scientists and engineers are always looking for ways to reduce the damage that might be caused when two objects collide.

null

Why would scientists study collisions in sports?

To force players to quit.

To reduce injury and improve performance.

To make games last longer.

To add more players to teams.

Let’s take a look at another example. You witness a head-on collision between a large semi-truck and a small sports car. Both were driving the speed limit, approximately 25 miles per hour.

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You notice the semi-truck appears to have sustained very little damage while the sports car appears truly beat up.

If they were going the same speed and we know that Mr. Newton claims forces are equal and opposite, then why didn’t both cars have the same amount of damage?

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1

Why did the semi-truck sustain less damage than the sports car?

The sports car was old and weak.

They collided at different speeds.

It has more mass and structural strength.

The truck driver braked suddenly.

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What happens to forces in a collision according to Newton's third law?

Forces are equal and opposite.

Forces depend on car types involved.

They cause only one vehicle to move.

Only the smaller car feels the force.

What happens when you push against a wall?

The wall pushes back with equal force.

The wall remains still and does nothing.

Your push is stronger than the wall's force.

You push harder and the wall moves.

If a car hits a tree, what occurs?

The car applies force and the tree pushes back.

Only the car is affected by the impact.

The tree doesn't resist the car's force.

Only the tree applies a force

What happens when you kick a soccer ball?

The ball pushes back with the same force.

The ball moves with no force.

The ball doesn't move at all.

You move, but the ball doesn't.

Why does the soccer ball move when kicked?

You are pushed back harder than the ball.

It moves because of gravity.

It is pushed by your foot only.

It requires less force due to its lower mass.

What does Newton's Third Law state about forces?

Only one object pushes back.

Forces always cause movement.

Only heavy objects experience reaction forces.

For every action, there is an equal and opposite reaction.

Why don't you move when you kick the ball?

You have more mass than the soccer ball.

The ball doesn't push back hard enough.

You are too light to be moved.

You kick too softly.

What happens to forces in a collision according to Newton's third law?

Forces are equal and opposite.

Forces depend on car types involved.

They cause only one vehicle to move.

Only the smaller car feels the force.

What determines an object's momentum?

Time in motion of the object.

Speed and distance traveled.

Mass and acceleration of the object.

Weight and height of the object.

Why does the semi-truck have more momentum than the sports car?

It is more aerodynamic.

It has a higher mass than the sports car.

It travels at a slower speed.

It has a larger volume.

What happens when two cars collide with equal forces?

Momentum increases for both cars.

The car with less momentum takes more damage.

Both cars take equal damage.

The larger car is always unharmed.

Which statement is true about forces in a collision?

Only one object experiences force.

Forces are equal and opposite in direction.

Forces are always unbalanced in a crash.

Larger objects exert greater force.

What force helps prevent the sports car from moving backward?

The weight of the car itself

The speed of the collision

Air resistance from the car

Friction with the road surface.

What does gravity do in this scenario?

Has no effect on the car

Pulls objects toward the center of Earth.

Pushes objects away from Earth

Increases the car's speed during a crash

How does friction affect the car’s momentum?

It increases the car's momentum

It only applies when the car is parked

It decreases the car's momentum significantly.

It has no effect on momentum

What role does the ground play in this example?

Causes the car to slide easily

Provides resistance against the car's movement (friction).

Has no interaction with the car

Absorbs all the car’s energy

What happens when air exits the back of the balloon?

The balloon falls to the ground.

The balloon stays still.

The balloon moves sideways.

The balloon moves forward.

Why does the balloon fly when air is released?

Air pushes out, causing forward motion.

Air pushes up, causing it to float.

The balloon is lighter without air.

Air is trapped inside, creating pressure.

In which direction does the balloon move when air is released?

Downward, due to weight.

Forward, opposite to the air direction.

Backward, with the air.

Upward, against gravity.

What scientific principle explains the balloon's movement?

Newton's third law of motion.

Gravity acting on the balloon.

Friction from the ground.

Air resistance holding it back.

What is the normal force in relation to gravity?

It pulls objects downwards.

It is the force of gravity itself.

It counteracts the force of gravity.

It is not related to gravity.

What does the ground do when you stand on it?

Pushes up against your feet.

Pulls you down with gravity.

Pulls you sideways.

Offers no resistance at all.

Which scientific law describes action and reaction forces?

Newton's law of inertia.

Newton's third law of motion.

Newton's law of universal gravitation.

Newton's first law of motion.

What would happen without the normal force?

You would fall toward the center of the earth.

You would remain still.

You would float away into space.

You would feel lighter.

What force causes the gun to recoil after shooting?

Gravity acting on the bullet.

The force of the bullet exiting the barrel.

The gun's weight pushing down.

Wind resistance on the bullet.

What injury can happen when firing a scoped gun incorrectly?

A bruise or cut near the eye.

A broken arm from the recoil.

A headache from the noise.

A sprained ankle from standing.

What is the main cause of the injury shown after shooting?

The scope is too heavy for the gun.

The bullet travels too fast during firing.

The shooter aims incorrectly and misses.

The gun recoils against the shooter's face.

What is one effect of Newton's Third Law in shooting?

Every action has an equal and opposite reaction.

A bullet changes direction in mid-air.

The gun becomes lighter when fired.

A bullet travels at the speed of sound.