Gravity & Newton's Laws Check 1/26

If you were able to travel to another planet, your weight would change. What would happen to your mass? Why?

My mass would remain constant because it is not affected by the magnitude of gravity.

What are each of the laws simplified?

Newton's 1st Law - Things keep doing what they are doing Newton's 2nd Law - Force = mass x acceleration Newton's 3rd Law - Action/Reaction

The force needed to change motion depends on the object's...

mass and acceleration

How does changing the speed of your hand hitting the desk affect the force of your hand?

The faster your hand moves, the more acceleration, and your hand hits the table with more force.

How does pushing a cart represent Newton's 2nd Law?

The greater the mass of the cart, the slower the acceleration and the greater the force needed is.

What is weight?

the force of gravity on an object

As long as the forces were balanced on the object,...

the object did not move.

If the boy pushing on the trampoline is the action force, what would provide the reaction force?

The trampoline on the boy.

Newton's 1st Law of Motion deals with forces that are...

balanced

What is inertia?

the resistance an object has to a change in its state of motion

An 2-kg object is moving horizontally with a speed of 4 m/s. How much net force is required to keep the object moving at this speed and in this direction?

0N

Imagine a place in the cosmos far from all gravitational and frictional influences. Suppose that an astronaut in that place throws a rock. 1. The rock will gradually stop 2. Continue in motion in the same direction at constant speed.

2. Continue in motion in the same direction at constant speed.

Rephrase Newton's 1st Law of Motion

All objects can be described as "keep on doing what they're doing"

Briefly summarize Newton's 2nd Law

An object accelerates when an unbalanced force is exerted on it; this acceleration has a direct relationship with the strength and direction of the net force as well as the mass of the object.

Imagine you have two identical baskets. Basket A is empty, basket B is full of candy. Which basket would need more force to lift? Explain, using newton' 2nd law.

Basket B would require more force to lift the basket. Newton's 2nd Law states that an "The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object." This means it would require more force to lift an object with a greater mass. Since Basket B has a greater mass, it will require more force to lift the basket.

"While riding a skateboard (or wagon or bicycle), you fly forward off the board when hitting a curb or rock or other object that abruptly halts the motion of the skateboard". Explain how Newton's 1st Law of Motion is shown in this example.

Before I hit a rock or another object that stops the motion of my skateboard, I am in motion at a constant speed and in the same direction. This means the forces around me are balanced. But, when I hit the rock or any object that stops the motion of my skateboard, the forces suddenly become unbalanced. Since Newton's First Law of Motion says that an object in motion will remain in motion unless an unbalanced force acts upon it, I will remain in motion until an unbalanced force acts upon the skateboard or me. Since I was still in motion when I hit the rock but since the skateboard was not, I continued to move forward but the skateboard did not.

If a fly were to hit a moving truck, which object exerted a larger force?

Both are equal.

While driving down the road, an unfortunate bug strikes the windshield of a bus. Quite obviously, this is a case of Newton's third law of motion. The bug hit the bus and the windshield hit the bus. Which of the two forces is greater: the force on the bug or the force on the bus?

Both forces are equal. "For every action, there is an equal...(equal!) The fact that the firefly splatters only means that with its smaller mass, it is less able to withstand the larger acceleration resulting from the interaction. ."

What is Newton's 3rd Law?

For every action there is an equal and opposite reaction.

Formula for Newton's 2nd Law

Force = mass x acceleration

What is gravity?

Force of attraction between 2 objects

What is the force that prevents you from being pulled into outer space?

Gravity

Mr. Wegley spends most Sunday afternoons at rest on the sofa, watching pro football games and consuming large quantities of food. What effect (if any) does this practice have upon his inertia? Explain.

His inertia will increase because his mass is increasing. Since inertia increases as mass increases, his inertia will increase.

Mac and Tosh are arguing in the cafeteria. Mac says that if he flings the Jell-O with a greater speed it will have a greater inertia. Tosh argues that inertia does not depend upon speed, but rather upon mass. Who do you agree with? Explain why.

I agree with Tosh because inertia depends only on mass. The greater the mass, the more inertia. "Momentum is another quantity in Physics which depends on both mass and speed. Momentum will be discussed in a later unit."

What do all objects that have mass have?

If something has mass, it has a gravitational pull.

What is Newton's First Law of Motion also called?

Law of Inertia

What does inertia depend on?

Mass

What two factors affect the amount of gravity on objects?

Mass and distance

What is mass?

Mass is the amount of matter in an object. (The amount of stuff, particles, atoms, etc.) Mass is ALWAYS constant

According to Newton's 3rd Law, do the forces act on the same object?

No. Opposite directions according to Newton's 3rd Law

Ben Tooclose is being chased through the woods by a bull moose which he was attempting to photograph. The enormous mass of the bull moose is extremely intimidating. Yet, if Ben makes a zigzag pattern through the woods, he will be able to use the large mass of the moose to his own advantage. Explain this in terms of inertia and Newton's first law of motion.

Since the moose has a large mass, he will have a large inertia. This means Ben, who has a smaller inertia due to having less mass, can make quicker changes in direction, or change his state of motion more easily than the moose.

Why does a ball bounce back up?

The ball bounced back up because the earth pushed back with an equal force. The ball has a smaller mass, so its acceleration was larger.

Between the balloon and the ground, think about which has the most mass. Use your answer to explain why the balloon bounced back up.

The balloon bounced back up because of Newton's 3rd Law of Motion. Newton's 3rd Law says that "For every action, there is an equal and opposite reaction." This means the magnitude of the force applied to the ground by the balloon is equal to the magnitude of the force applied to the balloon by the ground. But the reason why the balloon bounces back up and not the table is due to inertia. Inertia is the resistance an object has to a change in its state of motion. Inertia is directly related to mass and the greater the mass, the greater the inertia and the greater the resistance. Since the ground has a far greater mass than the balloon, it has a far greater inertia and thus, a far greater resistance to change in its state of motion.

Two bricks are resting on the edge of the lab table. Shirley Sheshort stands on her toes and spots the two bricks. She acquires an intense desire to know which of the two bricks are most massive. Since Shirley is vertically challenged, she is unable to reach high enough and lift the bricks; she can however reach high enough to give the bricks a push. Discuss how the process of pushing the bricks will allow Shirley to determine which of the two bricks is most massive. What difference will Shirley observe and how can this observation lead to the necessary conclusion?

The bricks have mass and thus have inertia. If Shirley gives them a push, then the bricks will have a resistance to the push. The brick with the greater mass will have the most inertia which will also be the one with the most resistance.

If you pick up an object, what type of force caused the object to change its motion?

Unbalanced

Newton's 2nd Law says that objects stop "doing what it's doing" when the forces become...

Unbalanced

How does riding a roller coaster show Newton's 1st Law?

When you go down after going up, the roller coaster goes down but you continue to move forward. So, for a second, we continue to move forward but the cart moved down.

How is Newton's 3rd Law used in swimming?

When you push against the water, you exert a force on the water and it exerts a force back on you. This causes you to accelerate. Both the water and the swimmer exert equal magnitude of forces but in opposite directions.

Think about when you hit your hand on the table. Did it hurt? Why?

When your hand hits the table with more force, the table hits your hand back with the same amount of force, just in the opposite direction; the table exerted an equal/opposite force on you

Is gravity a force?

Yes

If you jump in the air, do you exert a gravitational force on the earth?

Yes. Anything that has mass exerts a gravitational force.

If you jump in the air, does the earth exert a gravitational force on you?

Yes. Anything that has mass exerts a gravitational force.

Supposing you were in space in a weightless environment, would it require a force to set an object in motion?

Yes. Objects in space have mass and if they have mass, then they have inertia, the resistance of an object to change its state of motion. So, a force must be used to cause the stationary object to be in motion.

Are you attracted to the objects around you?

Yes. Since everything has mass, everything is attracted to one another.

The size of the forces on the first object _________ the size of the force on the second object. The direction of the force on the first object is _________ to the direction of the force on the second object. Forces ________ come in pairs - equal and opposite action-reaction force pairs.

equals, opposite, always

When the ball was moving down the lane, what force slowed the ball down, and in what direction was that force?

friction, acting opposite to the ball's motion.

When the car you are in suddenly stops, you keep moving because you have ___________.

inertia

Since Earth has a larger mass than a marble, the Earth's gravitational pull is...

larger than the marble's force

In order to leave Earth's pull, the force needed to leave must be __________ gravity.

more than

Rockets are unable to accelerate in space because...

nonsense! Rockets do accelerate in space.

Forces are balanced: objects at rest ->____________; objects in motion -> ___________

stay at rest; stay in motion

In the top picture (below), a physics student is pulling upon a rope which is attached to a wall. In the bottom picture, the physics student is pulling upon a rope which is attached to an elephant. In each case, the force scale reads 500 Newtons. The physics student is pulling...

the same force in each case.

The more mass something has, ...

the stronger the gravitational force.

The closer together objects are, ...

the stronger the gravitational pull

According to Newton, whenever objects A and B interact with each other,...

they exert equal but opposite forces upon each other

Earth's gravity pulls items...

towards the center of the earth