Exam 1: Chapter 3 and 4

Question 1

What is Newton’s first law of physics?

Answer 1

The law of inertia

Question 2

What does Newton’s first law state?

Answer 2

It states that a body will maintain in a state of rest or constant motion unless acted on by an external force that changes that state.

Question 3

What is linear momentum?

Answer 3

Linear momentum is the quantity of motion. It is measured as the product of a body’s mass and its velocity.

M = mv

Question 4

Will a static object have a momentum?

Answer 4

No, because it is not moving.

Question 5

Is momentum a scalar or vector quantity?

Answer 5

Momentum is a vector quantity, therefore, it has a magnitude and a direction. It will be able to follow the rules of vector composition and resolution.

Question 6

What is another name for Newton’s first law of physics?

Answer 6

The principle of conservation of momentum.

Question 7

What are two types of collisions?

Answer 7

Perfectly ELASTIC impact and perfectly plastic impact.

Question 8

What is an impact?

Answer 8

A collision characterized by an exchange of a large force during a small time interval.

Question 9

Explain a perfectly elastic impact.

Answer 9

An impact during which the velocity of the system is CONSERVED. (think bouncy ball).

Question 10

Explain a perfectly plastic impact.

Answer 10

An impact resulting in the TOTAL LOSS of system velocity. (think pudding).

Question 11

In most situations, are collisions elastic or plastic?

Answer 11

Neither, they are a combination of both.

Question 12

What is the coefficient of restitution?

Answer 12

It describes the relative elasticity of an impact. It is typically given as a number that serves as an index of elasticity for colliding bodies.

Question 13

What is the variable for the coefficient of restitution and its equation?

Answer 13

Coefficient of restitution :
-e = relative velocity after impact / relative velocity before impact

When two bodies undergo a direct collision, the difference in their velocities immediately after impact is proportional to the difference in the velocities immediately before impact.

Question 14

What was Newton’s second law of physics?

Answer 14

The law of acceleration.

A force applied to a body causes an acceleration of the body of a magnitude proportional to the force, in a direction of the force, and inversely proportional to the body’s mass.

F= ma

Question 15

If momentum is conserved, how do we add or subtract momentum to a system?

Answer 15

Impulse

Question 16

What is impulse?

Answer 16

Impulse is a net force acting over some interval of time applied to a system

Question 17

What is the equation for impulse?

Answer 17

Impulse = force x time = change in momentum

Question 18

If you were to want to increase momentum, what would you do?

Answer 18

You would either apply more force or apply the force over a longer period of time.

Ex. throwing or striking a ball

Question 19

If you were to want to decrease momentum, what would you do?

Answer 19

You would apply less force or decrease the period of time

Ex. Safety equipment, catching a fastpitch baseball

Question 20

What is Newton’s third law of physics?

Answer 20

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

When one body exerts a force on a second, the second body exerts a reaction that is equal in magnitude and opposite in direction.

Question 21

Define work and what is the equation for work?

Answer 21

Work is defined as a force applied against a resistance, multiplied by the displacement of the resistance in the direction of the force.

W = F x d

Question 22

What are two types of work?

Answer 22

Positive work and negative work.

Question 23

Explain positive work.

Answer 23

Positive work is when the net muscle torque and the direction of angular motion at a joint are in the SAME DIRECTION.

Example: Pushing the barbell up. You are pushing up, and the barbell is moving up in the same direction.

Question 24

Explain negative work.

Answer 24

Negative work is when the net muscle torque and the direction of angular motion at a joint are in OPPOSITE DIRECTION.

Example: “Pushing” the barbell as it is going down. You are pushing up on the bar, the barbell is going down in the opposite direction.

Question 25

What is the units for work?

Answer 25

Joules (J)

Question 26

What is energy?

Answer 26

Energy is defined as the capacity to do work.

Question 27

What is mechanical energy?

Answer 27

The capacity to do mechanical work. (Units are the same, Joules (J)).

Question 28

What is kinetic energy?

Answer 28

The energy of an object or person in motion.

Question 29

What is potential energy?

Answer 29

The energy that is stored at a particular position (height).

Question 30

What is a special type of potential energy?

Answer 30

Strain Energy (SE) or Elastic Energy.

Question 31

What is Strain Energy?

Answer 31

Strain energy is the capacity to do work by virtue of a deformed body’s return to its original shape. (i.e. a spring diving board).

Question 32

What is the formula for Strain Energy (SE)?

Answer 32

SE = ½ kx2

Where k is the spring constant; representing the material’s relative stiffness or ability to store energy on deformation and x is the distance over which the material is deformed.

Question 33

Work is equal to what in terms of energy?

Answer 33

The work of a force is equal to the change in energy that it produces on the object acted on it.

W = PE + KE + TE

Question 34

About how much energy is consumed by muscles into work?

Answer 34

25%

Question 35

What is impulse?

Answer 35

It is the change in momentum.

To create a large change in momentum, a large force must be applied over a long time.

Question 36

What is power and what is the formula for power?

Answer 36

Power is the rate of work production.

Work divided by time. P = W / t

Units is Watts (W).