# Physics

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Object A has a small mass. Object B has a large mass. If the same net force is applied to A and B, which one will accelerate at a greater rate? (Mr. Maine)
Object A
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Why was Copernicus reluctant to publish his ideas? (Ethan)
He was afraid he would be persecuted by the church, since his ideas went against the church's teachings.
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What is the effect of friction on a moving object? How is the object able to maintain a constant speed when friction acts upon it? (Cooper)
Friction pushes on an object in the opposite direction it is moving, creating resistance against the object's motion, and ultimately slowing it down to a stop. Galileo said that if an object didn't have a force of friction acting upon it, it would move forever. The object is able to maintain a constant speed when friction acts upon because the object has exactly the right force to cancel out the friction force.
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What was the distinction Aristotle made between "natural motion" and "violent motion"? (Clara
): Natural motion is more up and down, like smoke rising. The moving object is going to its natural resting place. Violent motion is motion that is forced, for example a bowling ball rolling because of force from an arm. Violent motion is the result of a pulling/pushing force.
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What does Newton's law of Inertia (his first law of motion) say? (Colter;)
Newton's first law says that an object in motion will stay in motion and an object at rest will stay at rest unless there are external forces that cause it to move. If there are no external forces acting on a moving object, it will move at a constant speed in a straightline.
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What does Newtons 2nd law of motion say? (Jake M.)
It states that acceleration is directly proportional to net force, and that acceleration is inversely proportional to mass.
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Does the law of inertia pertain to moving objects, objects at rest, or both? (Ethan)
Both.
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If you were in a spaceship and fired a cannonball into frictionless space, how much force would have to be exerted on the ball to keep it going? (Clara)
You would not need to exert any force on to the cannonball because there is no friction in space to stop it.
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The law of inertia states that no force is required to maintain motion. Why, then, do you have to keep pedaling to keep your bike moving at a constant speed? (Clara
):You have to keep pedaling because of friction. There is friction between your wheels and the ground, as well as air resistance, which will slow down and eventually stop your bike. To keep the bike going, you must continue to exert force on to it. The force should be equal to the amount of friction in order to keep the bike moving at a constant speed.
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What is the equation for Newton's 2nd Law? (Ethan)
Acceleration = Net force/Mass
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When we did the analysis of the Newton's Car activity, we said that the distance the car moved after the unbalanced force was applied to it was directly related to the acceleration of the car. Why was it necessary to say this? (Mr. Maine)
Newton's 2nd Law of motion describes the relationship between acceleration, net force, and mass. It does not include distance. So in order to connect our experiment to Newton's 2nd Law, we had to say that the distance is directly related to the acceleration.
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What is inertia, according to Galileo? (Cooper)
Inertia is the resistance that an object has to a change in its current state of motion.
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The speed of a ball increases as it rolls down an incline, and the speed decreases as the ball rolls up an incline. What happens to the speed on a smooth horizontal surface? (Avi)
The ball moves at a constant speed and in a straight line. This is an idealized situation that Galileo thought about but isn't realistic on Earth because of friction.
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What is Newton's First Law of Motion (Law of Inertia)? (Avi)
Every object continues in its state of rest, or of motion in a straight line at constant speed, unless it is compelled to change that state by unbalanced forces exerted upon it.
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If an object falls towards the earth, does the earth fall towards the object? (Thomas)
Yes. This phenomenon isn't noticeable because the earth has such a large mass that it barely moves when pulled by such a relatively small force.
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What is Newton's Third Law of Motion? (Walter)
Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.
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Using the third law of motion, how do cars on earth and rockets in space move differently. (Walter)
The car's tire pushes on the road. In response, the road pushes on the tire pushing it forward. The rocket shoots out gas (fuel). In response, the fuel pushes the rocket.
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Why don't action and reaction forces cancel? (Walter)
Each force applies on a different object. For example, when the rifle fires, the rifle pushes the bullet forward. Then the bullet pushes the rifle backwards. Each force is acting on a different object. It will only cancel if the same magnitude of force is applied on one object from opposite directions.
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Why did the iPad resting on the floor not fall through the floor? (Walter)
Two forces were acting on the iPad. One was the gravitational force pulling down. The other was the floor pushing up. These forces were equal magnitude in opposite directions. This creates a balance of forces. Therefore they canceled each other out and the iPad didn't move.
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If you push a box with a force of 10N and your friend helps you and pushes the box in the same direction with a force of 5N, what is the net force? (Nina)
The net force is 15 N.
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If you push a box with a force of 10N and your friend pulls the box in the opposite direction with a force of 5N, what is the net force? (Nina)
The net force is 5 N.
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What is meant by the net force that acts on an object? (Samy)
Net force is the combination of all the forces that act on an object.
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Suppose a cart is being moved by a certain net force. If the net force is doubled, by how much does its acceleration change? (Samy)
The acceleration is doubled since net force and acceleration are directly proportional.
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Suppose a cart is being moved by a certain net force. If a load is dumped into the cart so its mass is doubled, by how much does the acceleration change? (Samy)
The acceleration is half as much since mass and acceleration are inversely proportional.
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Distinguish the concepts of directly proportional and inversely proportional. (Samy)
If one thing is directly proportional to something else, as one increases by a certain factor (such as doubling), the other will increase by the same factor (which means it will double). If one thing is inversely proportional to something else, as one thing increases by a certain factor, the other thing will decrease by the inverse of that factor. For example, in the equation a = Fnet / m , if the mass doubles while the net force stays the same, the acceleration will decrease by a factor of Β½.
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If a large box Is being leaned on by a man with 10 newtons of force, a woman is pulling on the box with 5 newtons of force from the opposite side of the box, and the carpet under the box is offering 5 newtons of friction, how much net force is applied to the box?
The Net Force is 10 N.
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What would happen to the net force if the box's mass is reduced by 50%? Explain why the mass affects the net force the way it does using equalities, inverse proportions, direct proportions or improportionalities.
The Net Force is still 10 N.This was a trick question. Forces acting upon an object are not affected by the mass of said object. The acceleration of the box can be affected by changing the mass of the object, but you can't change the power of a force simply by changing a mass, they are not connected. It is similar to saying: if I gain weight, the force of people's punches will decrease.
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What would be a scenario in which an object is being pushed with 10 N of force and and is also being pulled with 10 N of force, yet the Net Force is equal to 20N? (Simon)
If the object is being pushed and pulled in the same direction. Do not assume that just because an object is being pushed and pulled with the same amount of force that the object has no Net Force. In order for an object be pushed and pulled on and have a Net Force of 0N, is if the object is being pushed and pulled in opposite directions with the same force.
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When swimming, you push the water backward - call this action force. Then what exactly is the reaction force? (Lauren)
The reaction force is the water pushing you forward.
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In the interaction between a hammer and the nail it hits, is a force exerted on the nail? On the hammer? How many forces occur in this interaction? (Lauren)
The hammer exerts a force on the nail and the nail exerts a force on the hammer. Two forces occur in this interaction.
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Complete the sentence: When the forces acting on an object at rest are balanced...
The object stays at rest.
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Complete the sentence: When the forces acting on an object in motion are balanced...