### Which Statement Is True About Newton’S First Law Of Motion?

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• 6 Newton’s First Law – AP Physics 1 Possible Answers: Correct answer: Explanation : Newton’s first law states that an object in motion tends to stay in motion unless if acted upon by a net force. This means that if friction is not being accounted for, there is no net force required to keep an object moving if it’s in motion.

A net force is only required to change an object’s motion. The 500 kg object is moving at a constant velocity; therefore, there is no net force (0 Newtons) acting on the object. All of the following statements are true. Which of them is NOT explained by Newton’s first law of motion? Possible Answers: If I’m riding a skateboard, it doesn’t spontaneously reverse directions.

Dropping a box causes it to accelerate downwards. A baseball thrown in space will keep moving in the same direction until it hits something. A ball rolling straight down a tilted plane hill won’t veer left or right unless something pushes it. A book lying on a desk doesn’t start moving without an external force.

• Newton’s first law of motion refers to objects with no external forces acting on them. Objects with no external forces will maintain the same velocity, meaning that
• (1) if they are not moving, they will continue not moving
• (2) if they are moving, they will keep moving with the same speed and direction

The answer “Dropping a box causes it to accelerate downwards” refers to a box with a force acting upon it—the force of gravity. Also, the box is accelerating, unlike objects referred to by Newton’s first law of motion, which have constant velocities. A spaceship travels in the vacuum of space at a constant speed of Ignoring any gravitational forces, what is the net force on the spaceship? Possible Answers: Correct answer: Explanation : In a vacuum, there is no friction due to air resistance. Newton’s first law states that an object in motion stays in motion unless acted upon by a net force.

Thus the spaceship will travel at the constant speed (zero acceleration) of indefinitely and the net force on the spaceship must be zero. This can also be shown mathematically: You are traveling on an airplane at constant speed of 650mph. Your friend is traveling in his car at a constant speed of 60mph.

Who experiences a larger acceleration? Possible Answers: Cannot be determined; we must know the force due to friction Neither you nor your friend Correct answer: Neither you nor your friend Explanation : Since both you and your friend are traveling at a constant speed, the acceleration of you and your friend is zero.

Thus, neither you nor your friend experiences any acceleration. This can be shown mathematically using the equation for acceleration: Since there is no change in velocity over time acceleration is zero. Also note that when acceleration is zero, so is the net force. You are sitting in a car, at rest, when another car rear ends your vehicle.

Why do you and the passengers experience a whiplash, in terms of Newton’s laws of motion? Possible Answers: A larger/more massive object means a larger inertia An object at rest tends to stay at rest Acceleration is the time derivative of velocity Correct answer: An object at rest tends to stay at rest Explanation : Because an object at rest tends to stay at rest, when your car is hit your body/neck will ‘want’ to stay where it was.

1. This will cause your body and neck to ‘whip’ as it will take time for it to speed up from being hit.
2. A passenger in an elevator has a mass that exerts a force of 100N downwards.
3. He experiences a normal force upwards from the elevator’s floor of 120N.
4. What direction is he accelerating in, if at all, and at what rate? Possible Answers: upwards upwards downwards upwards Correct answer: upwards Explanation : The acceleration of the person in the elevator is determined by the net forces and his/her mass.

The net force is calculated to be 20N upwards. To find the mass of the passenger, use the following formula:

1. Then, to find the net acceleration, use Newton’s second law.

A 1675 kilogram car is moving to the right at a constant velocity of, What is the net force exerted on the car? Possible Answers: Correct answer: Explanation : Recall Newton’s first law of motion: an object will remain in its state of uniform motion unless acted upon by an external force.

• If the box is moving at a constant velocity, we know that the sum of the forces acting up and down the inclined plane must add to zero. If the only forces acting are gravity and friction, we can show:
• We can gain information about the normal force by looking at the forces acting perpendicular to the plane, shown by:
• Putting all of this together lets us write the following expression for the forces in acting along the plane, and finally, our answer:

A spacecraft is deep in space and motionless. Then, the spacecraft separates into two sections going in opposite directions. The first has a mass of and is moving with a magnitude of velocity of, The second has a mass of, Determine the magnitude of velocity of the second section. Possible Answers: Correct answer: Explanation :

1. Use conservation of momentum:
2. Plug in values.
3. Solve for :

A skydiver of mass has reached terminal velocity at, Estimate the force of wind resistance she is experiencing. Possible Answers: Correct answer: Explanation :

• If the diver has reached terminal velocity, her acceleration is,
• Thus, according to Newton’s second law:
• Her net force is equal to zero.
• The only forces acting on her are gravity and wind resistance, which must add up to zero.
• Where is pointing down and thus negative
• Plug in values:
• Solve for

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### Why do we need Newton’s first law of motion?

Air resistance, gravity, and friction, all need to be taken into account when explaining why something is slowing down. These forces influence the velocity of an object.

• Newton’s first law explains how things move and how forces work on their movement, which makes it an extremely important discovery.
• If we were to place an object into space, we could observe how it behaves without any external influences.
• The force that is exerted upon an object can be either external or internal.

Before Newton’s laws explained how the majority of things in the world work to us, people were not aware of why objects were slowing down. They believed that they did so by themselves because they tend to do so. However, people back then did not understand the forces that work in nature or how they work.

## What are the three Newton laws of motion?

An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force. – Newton’s first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force.

## What does Newton’s 1st law of motion state?

Review Newton’s Laws of Motion –

 1. Newton’s First Law of Motion (Inertia) An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force. 2. Newton’s Second Law of Motion (Force) The acceleration of an object depends on the mass of the object and the amount of force applied. 3. Newton’s Third Law of Motion (Action & Reaction) Whenever one object exerts a force on another object, the second object exerts an equal and opposite force on the first.

#### What does Newton’s first law of motion claim?

An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force. – Newton’s first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force.