Lesson 1: Newton's First Law Of Motion

1. __________ is the tendency of an object to resist changes in its state of motion.

Inertia is the tendency of an object to resist changes in its state of motion. This means that an object at rest will remain at rest, and an object in motion will continue moving at a constant velocity, unless acted upon by an external force. Inertia is a fundamental property of matter and is related to the mass of an object. The greater the mass, the greater the inertia, and the more force is required to change its motion. Inertia is a concept that is often observed in everyday life, such as when a car suddenly stops and passengers lurch forward due to their inertia.

Explanation

Inertia is the tendency of an object to resist changes in its state of motion. This means that an object at rest will remain at rest, and an object in motion will continue moving at a constant velocity, unless acted upon by an external force. Inertia is a fundamental property of matter and is related to the mass of an object. The greater the mass, the greater the inertia, and the more force is required to change its motion. Inertia is a concept that is often observed in everyday life, such as when a car suddenly stops and passengers lurch forward due to their inertia.

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2. _________ is the speed with a direction.

Velocity is the correct answer because it refers to the speed of an object in a specific direction. It is a vector quantity that includes both magnitude (speed) and direction, making it different from speed, which only considers the magnitude of an object's motion. Therefore, velocity accurately describes the speed with a direction.

Explanation

Velocity is the correct answer because it refers to the speed of an object in a specific direction. It is a vector quantity that includes both magnitude (speed) and direction, making it different from speed, which only considers the magnitude of an object's motion. Therefore, velocity accurately describes the speed with a direction.

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3. ____________ is that quantity which depends solely upon inertia.

Mass is the quantity that depends solely upon inertia. Inertia is the resistance of an object to changes in its motion, and mass is a measure of this resistance. The more mass an object has, the greater its inertia and the harder it is to change its motion. Therefore, mass is the correct answer as it directly relates to the concept of inertia.

Explanation

Mass is the quantity that depends solely upon inertia. Inertia is the resistance of an object to changes in its motion, and mass is a measure of this resistance. The more mass an object has, the greater its inertia and the harder it is to change its motion. Therefore, mass is the correct answer as it directly relates to the concept of inertia.

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4. To determine if the forces acting upon an object are balanced or unbalanced, an analysis must first be conducted to determine what forces are acting upon the object and in what direction.

True

False

The explanation for the given correct answer is that in order to determine if the forces acting upon an object are balanced or unbalanced, it is necessary to analyze and identify the forces that are acting upon the object and the direction in which they are acting. This analysis helps in understanding the overall net force acting on the object, which determines whether the forces are balanced (resulting in no acceleration) or unbalanced (resulting in acceleration). Therefore, the statement is true.

Explanation

The explanation for the given correct answer is that in order to determine if the forces acting upon an object are balanced or unbalanced, it is necessary to analyze and identify the forces that are acting upon the object and the direction in which they are acting. This analysis helps in understanding the overall net force acting on the object, which determines whether the forces are balanced (resulting in no acceleration) or unbalanced (resulting in acceleration). Therefore, the statement is true.

5. Imagine a place in the cosmos far from all gravitational and frictional influences. Suppose that you visit that place (just suppose) and throw a rock. The rock will

Gradually stop.

Continue in motion in the same direction at constant speed.

Will not move.

None of the above.

According to Newton's first law, the rock will continue in motion in the same direction at constant speed.

Explanation

According to Newton's first law, the rock will continue in motion in the same direction at constant speed.

6. 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?

Mac

Tosh

None of the above.

Tosh is correct. Inertia is that quantity which depends solely upon mass. The more 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.

Explanation

Tosh is correct. Inertia is that quantity which depends solely upon mass. The more 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.

7. Several of Luke's friends were watching the motion of the falling cat. Being "physics types", they began discussing the motion and made the following comments. Indicate whether each of the comments is correct or incorrect?

Upon hitting the water, the cat will bounce upwards due to the upward force.

True

False

Once the cat hits the water, the forces are balanced (50 N down and 50 N up). The cat would only bounce upwards if the water applied an upward force greater than 50 N. As stated in the problem, the water applies only 50 N of upward force. Furthermore, the upward force would first contribute to slowing the cat down (an upward acceleration) before it could begin to actually move it upward.

Explanation

Once the cat hits the water, the forces are balanced (50 N down and 50 N up). The cat would only bounce upwards if the water applied an upward force greater than 50 N. As stated in the problem, the water applies only 50 N of upward force. Furthermore, the upward force would first contribute to slowing the cat down (an upward acceleration) before it could begin to actually move it upward.

8. __________, a premier scientist in the seventeenth century, developed the concept of inertia.

Galileo, a premier scientist in the seventeenth century, developed the concept of inertia. His experiments and observations challenged the prevailing belief that objects needed a force to keep moving. Galileo proposed that objects in motion would stay in motion unless acted upon by an external force, which is now known as the principle of inertia. This concept revolutionized the understanding of motion and laid the foundation for Newton's laws of motion. Galileo's contributions to physics and astronomy solidified his status as one of the most influential scientists in history.

Explanation

Galileo, a premier scientist in the seventeenth century, developed the concept of inertia. His experiments and observations challenged the prevailing belief that objects needed a force to keep moving. Galileo proposed that objects in motion would stay in motion unless acted upon by an external force, which is now known as the principle of inertia. This concept revolutionized the understanding of motion and laid the foundation for Newton's laws of motion. Galileo's contributions to physics and astronomy solidified his status as one of the most influential scientists in history.

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9. An object is said to be acted upon by an unbalanced force only when there is an individual force that is not being balanced by a force of equal magnitude and in the opposite direction.

True

False

An object is said to be acted upon by an unbalanced force when there is an individual force that is not being balanced by a force of equal magnitude and in the opposite direction. This means that if there is a force acting on an object that is not being cancelled out by an equal and opposite force, then the object will experience an unbalanced force. Therefore, the statement is true.

Explanation

An object is said to be acted upon by an unbalanced force when there is an individual force that is not being balanced by a force of equal magnitude and in the opposite direction. This means that if there is a force acting on an object that is not being cancelled out by an equal and opposite force, then the object will experience an unbalanced force. Therefore, the statement is true.

10. Several of Luke's friends were watching the motion of the falling cat. Being "physics types", they began discussing the motion and made the following comments. Indicate whether each of the comment(s) is correct or incorrect?

Upon hitting the water, the cat will accelerate upwards because the water applies an upward force.

True

False

Once the cat hit the water, the forces are balanced (50 N down and 50 N up). The upward force of the water on the cat is balanced by the downward pull of gravity. The cat will continue in motion at constant speed.

Explanation

Once the cat hit the water, the forces are balanced (50 N down and 50 N up). The upward force of the water on the cat is balanced by the downward pull of gravity. The cat will continue in motion at constant speed.

11. A 4.0-kg object is moving across a friction-free surface with a constant velocity of 2 m/s. Which one of the following horizontal forces is necessary to maintain this state of motion?

0 N

5 N

10 N

None of the above.

If an object is in motion, then it will stay in motion with those very same motion characteristics. It doesn't take any force to maintain that same state of motion. In fact, the presence of a force would "ruin" such a state of motion and cause an acceleration.

Explanation

If an object is in motion, then it will stay in motion with those very same motion characteristics. It doesn't take any force to maintain that same state of motion. In fact, the presence of a force would "ruin" such a state of motion and cause an acceleration.

12. ______________ states that "An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force."

Newton's First Law of Motion, also known as the law of inertia, states that an object at rest will remain at rest, and an object in motion will continue moving at a constant velocity in a straight line, unless acted upon by an unbalanced force. This means that an object will maintain its state of motion, whether it is at rest or moving, unless there is an external force causing a change in its motion. This law helps to explain why objects tend to resist changes in their motion and why it is necessary to apply force to start, stop, or change the direction of an object's motion.

Explanation

Newton's First Law of Motion, also known as the law of inertia, states that an object at rest will remain at rest, and an object in motion will continue moving at a constant velocity in a straight line, unless acted upon by an unbalanced force. This means that an object will maintain its state of motion, whether it is at rest or moving, unless there is an external force causing a change in its motion. This law helps to explain why objects tend to resist changes in their motion and why it is necessary to apply force to start, stop, or change the direction of an object's motion.

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

Yes.

No.

None of the above.

Absolutely yes!

Even in space objects have mass. And if they have mass, they have inertia. That is, an object in space resists changes in its state of motion. A force must be applied to set a stationary object in motion. Newton's laws rule - everywhere!

Explanation

Absolutely yes!

Even in space objects have mass. And if they have mass, they have inertia. That is, an object in space resists changes in its state of motion. A force must be applied to set a stationary object in motion. Newton's laws rule - everywhere!

14.

A group of physics teachers is taking some time off for a little putt-putt golf. The 15th hole at the Hole-In-One Putt-Putt Golf Course has a large metal rim that putters must use to guide their ball towards the hole. Mr. S guides a golf ball around the metal rim When the ball leaves the rim, which path (1, 2, or 3) will the golf ball follow?

1

2

3

None of the above.

The answer is 2. Once leaving the rim, the ball will follow an "inertial path" (i.e., a straight line). At the instant shown in the diagram, the ball is moving to the right; once leaving the rim, there is no more unbalanced forces to change its state of motion. Paths 1 and 3 both show the ball continually changing its direction once leaving the rim.

Explanation

The answer is 2. Once leaving the rim, the ball will follow an "inertial path" (i.e., a straight line). At the instant shown in the diagram, the ball is moving to the right; once leaving the rim, there is no more unbalanced forces to change its state of motion. Paths 1 and 3 both show the ball continually changing its direction once leaving the rim.

15. Several of Luke's friends were watching the motion of the falling cat. Being "physics types", they began discussing the motion and made the following comments. Indicate whether each of the comment(s) is correct or incorrect?

Once the cat hits the water, the forces are balanced and the cat will stop.

True

False

Once the cat hits the water, the forces are balanced (50 N down and 50 N up). However, an object in motion (such as the cat) will continue in motion at the same speed and in the same direction. When the cat strikes the water, it stops accelerating; yet it does not stop moving.

Explanation

Once the cat hits the water, the forces are balanced (50 N down and 50 N up). However, an object in motion (such as the cat) will continue in motion at the same speed and in the same direction. When the cat strikes the water, it stops accelerating; yet it does not stop moving.

16. A 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?

0 N

1 N

10 N

None of the above.

An object in motion will maintain its state of motion. The presence of an unbalanced force changes the velocity of the object.

Explanation

An object in motion will maintain its state of motion. The presence of an unbalanced force changes the velocity of the object.

17. Fred 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?

Fred's inertia stays the same!

Fred's inertia will decrease!

Fred's inertia will increase!

None of the above.

Fred's inertia will increase!

Fred will increase his mass if he makes a habit of this. And if his mass increases, then his inertia increases.

Explanation

Fred's inertia will increase!

Fred will increase his mass if he makes a habit of this. And if his mass increases, then his inertia increases.

18.

Which one of the velocity-time graphs best describes the motion of the cat? Support your answer with sound reasoning.

Graph A

Graph B

Graph C

None of the above.

Graph B is correct. The cat first accelerates with a negative (downward) acceleration until it hits the water. Upon hitting the water, the cat experiences a balance of forces (50 N downwards due to gravity and 50 N upwards due to the water). Thus, the cat will finish its motion moving with a constant velocity. Graph B depicts both the initial negative acceleration and the final constant velocity.

Explanation

Graph B is correct. The cat first accelerates with a negative (downward) acceleration until it hits the water. Upon hitting the water, the cat experiences a balance of forces (50 N downwards due to gravity and 50 N upwards due to the water). Thus, the cat will finish its motion moving with a constant velocity. Graph B depicts both the initial negative acceleration and the final constant velocity.

19.

Which one of the following dot diagrams best describes the motion of the falling cat from the time that they are dropped to the time that they hit the bottom of the pool? The arrows on the diagram represent the point at which the cat hits the water. Support your answer with sound reasoning.

Tape A

Tape B

Tape C

None of the above

Tape A is correct.

The cat first accelerates with a negative (downward) acceleration until it hits the water. Upon hitting the water, the cat experience a balance of forces (50 N downwards due to gravity and 50 N upwards due to the water). Thus, the cat will finish its motion moving with a constant velocity. Diagram A depicts both the initial downward acceleration and the final constant velocity.

Explanation

Tape A is correct.

The cat first accelerates with a negative (downward) acceleration until it hits the water. Upon hitting the water, the cat experience a balance of forces (50 N downwards due to gravity and 50 N upwards due to the water). Thus, the cat will finish its motion moving with a constant velocity. Diagram A depicts both the initial downward acceleration and the final constant velocity.

20. If the forces acting upon an object are balanced, then the object

Must not be moving.

Must be moving with a constant velocity.

Must not be accelerating.

None of these.

The answer could be A (but does not have to be A) and it could be B (but does not have to be B). An object having balanced forces definitely cannot be accelerating. This means that it could be at rest and staying at rest (one option) or could be in motion at constant velocity (a second option). Either way, it definitely is not accelerating - choice C of your four choices.

Explanation

The answer could be A (but does not have to be A) and it could be B (but does not have to be B). An object having balanced forces definitely cannot be accelerating. This means that it could be at rest and staying at rest (one option) or could be in motion at constant velocity (a second option). Either way, it definitely is not accelerating - choice C of your four choices.