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PHYS002A > Material from Midterm 2 to Final > Flashcards

Material from Midterm 2 to Final Flashcards

1
Q

Kinetic energy is energy associated with …

A

Motion

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2
Q

Potential energy is energy associated with …

A

Lifting things/gravity.

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3
Q

What does heat deal with?

A

Transfer of thermal energy.

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4
Q

What does work deal with?

A

Transfer of mechanical energy.

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5
Q

When is energy conserved in a system?

A

When the system is isolated from the environment, the energy is conserved.

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6
Q

How can energy be flown into and out of the system?

A

Via heat (transfer of thermal energy) and work (transfer of mechanical energy).

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7
Q

For the purposes of this class, energy is conserved within a system UNLESS …

A

Mechanical work is done on it by the environment. ΔEsys=W

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8
Q

What is the equation to keep in mind when dealing with work/kinetic energy?

A

Fx= Fcosθ=ma(x)

FxΔx= 1/2m(v final)^2-1/2m(v initial)^2

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9
Q

What is the equation for Kinetic Energy?

A

K=1/2mv^2 (in Joules). 1J= 1kgm^2/s^2

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10
Q

How can the work of something be regarded as if it is opposite the direction of motion?

A

Negative. ONLY work in the direction of motion is considered positive.

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11
Q

Work on a system results in _____.

A

A change in Kinetic Energy= ΔK

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12
Q

When something is said to be moving at a constant speed, what is its change in kinetic energy?

A
  1. Velocities are not changing, so kinetic energy is 0.
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13
Q

A force applied over some time period changes what value?

A

mv, being MOMENTUM

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14
Q

Is momentum a scalar or a vector? What are its units?

A

Vector; has positive and negative signs; units are kgm/s

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15
Q

Define Impulse

A

Change in an object’s momentum due to a force acting for some time.

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16
Q

Describe Everything about the Conservation of Momentum.

A

When two objects collide, they have a Newton’s 3rd Law Pair of forces between them. F2 on 1 is equal in magnitude to F1 on 2; their direction is the opposite. The 1st object adds momentum to the 2nd, while the 2nd takes away momentum from the first. SUM OF MOMENTA STAY THE SAME AT ANY GIVEN POINT. Momentum is only conserved when considering ALL the interacting objects.

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17
Q

When is momentum conserved?

A

When you are considering ALL of the interacting objects in the designated system of choice.

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18
Q

How do we choose the system in which momentum is conserved?

A

Ideally, we want a system where no external forces are acting on the object. If they are, we can zoom in on the instance where the objects are colliding. In most cases, the resulting force of the collision in that instance will be so large that we can ignore the other external forces.

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19
Q

Define Perfectly Inelastic Collisions

A

Collisions when objects collide and stick together.

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20
Q

What are some examples of inelastic collisions?

A

Car crashes-Dog catching a frisbee- Person jumping on skateboard.

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21
Q

What is a key thing to note about inelastic collisions?

A

Both objects have the SAME final velocity.

22
Q

In one dimension, what is the equation that involves momentum for inelastic collisions?

A

m1v1(i) + m2v2 (f)= (m1+m2)vf

23
Q

With momentum, what are two key things that need to be done?

A

Define a coordinate system and be mindful of signs.

24
Q

What happens with explosions?

A

Objects start at one mass and one velocity and end up with different masses and different velocities.

25
Q

What is the equation for determining momentum with explosions?

A

(m1+m2)vi= m1v1(f)+ m2v2(f)

26
Q

Define Elastic Collisions

A

Collisions where momentum and kinetic energy are conserved.

27
Q

With elastic collisions, how do you find the final velocity of object 1 in relation to its initial velocity?

A

v1(f)= ((m1-m2)/(m1+m2))v1(i)

28
Q

With elastic collisions, how do you find the final velocity of object 2 in relation to object 1’s initial velocity?

A

v1 (f)= (2m1)/(m1+m2) v1(i)

29
Q

If 2 objects are of the same mass with elastic collisions and the second one is at rest, what are the values of v1f and v2f?

A

v1f=0 and v2f=v1i

30
Q

If object one is of greater mass than object 2 and the second object is at rest, what are the values of v1f and v2f?

A

v1f=v1i and v2f=2v1i

31
Q

If object one is of less mass than object 2 and the second object is at rest, what are the values of v1f and v2f?

A

v1f= (-)v1i and v2f=0

32
Q

What is the equation for angular momentum?

A

L= Iω

33
Q

Explain everything important about the conservation of angular momentum

A

The total angular momentum of an isolated system is constant. The total final angular momentum is equivalent to the total initial angular momentum.

34
Q

When is the work of something regarded to be positive/negative?

A

When it is in the direction of motion, it’s positive. When it’s opposite the direction of motion, it’s negative.

35
Q

Work on a system results in a change in ______.

A

Kinetic Energy

36
Q

What is the equation for total work?

A

Kf-Ki

37
Q

What is theta when talking about work?

A

The angle between the force and the direction of displacement.

38
Q

How do you find work from a force vs. position graph?

A

Area under the curve.

39
Q

What are examples of dissipative forces?

A

Drag and friction

40
Q

What is the function of dissipative forces?

A

They transfer KE to thermal energy.

41
Q

Can static friction do work?

A

No, it cannot. Since SF is the force that is involved with the prevention of moving objects, there’s no displacement involved, making it unable to do work.

42
Q

What is the equation for the change in power?

A

Change in energy/change in time.

43
Q

What is the equation for the change in potential energy that’s related to work?

A

Change in PE= -Wint

44
Q

What is the formula for gravitational PE?

A

U=mgy

45
Q

What is there conservation of energy formula if there are no dissipative forces (Drag/Friction)?

A

Ki+Ui=Kf+Uf

46
Q

What is the formula for TE in PE diagrams?

A

TE= PE+KE

47
Q

Where are the turning points of the object in the PE graph?

A

Where PE=TE

48
Q

Where can the equilibrium positions be found on the graph of PE?

A

Where curve is flat.

49
Q

How can you tell if an equilibrium position is stable or not?

A

If concave up, it’s stable. If concave down, it’s unstable.

50
Q

How can you determine the final momentum of something when impulse is applied?

A

Impulse= Force Applied x Time. You take the initial momentum and add the impulse.

51
Q
A

PHYS002A (4 decks)

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