# Unit 3 Flashcards Preview

## Physics 1 > Unit 3 > Flashcards

Flashcards in Unit 3 Deck (52)
1
Q

impulse is equal to…

A

…change in momentum

2
Q

What do you need in order to cause a change in momentum?

A

Have to exert an impulse.

3
Q

Impulse equation

A
```impulse = force * time interval = Ft
Ft = change in momentum = (change in m*v)```
4
Q

Momentum equation

A

Momentum = mass * velocity = mv OR mass * speed

5
Q

Momentum

A

Inertia in motion

6
Q

A moving object can have a large momentum if it…

A

…has a large mass, a high speed, or both.

7
Q

What produces acceleration?

A

Force.

8
Q

Impulse

A

Change in momentum depends on the force that acts the length of time it acts.

9
Q

Decrease momentum

A

Extend the time of contact, reduce the force of the catch.

10
Q

The impulse required to bring an object to a stop and then to “throw it back again” is…

A

…greater than the impulse required merely to bring the object to a stop.

11
Q

Law of Conservation of Momentum

A

States that, in the absence of an external force, the momentum of a system remains unchanged.

12
Q

Whenever objects collide in the absence of external forces…

A

…the net momentum of both objects before the collision equals the net momentum of both objects after the collision.

13
Q

Elastic collision

A

When objects collide without being permanently deformed and without generating heat.

14
Q

Inelastic collision

A

A collision in which the colliding objects become distorted and generate heat during the collision.

15
Q

Equation conservation of momentum

A

net momentum(before collision) = net momentum(after collision)
OR
(net mv)before = (net mv)after

16
Q

Vector sum of momenta is…

A

…the same before and after a collision

17
Q

The force or impulse must be exerted on the object by something….

A

…outside the object.

18
Q

Momentum is conserved only when interacting objects move along…

A

…the same straight path

19
Q

With the absence of air resistance in space…

A

gravity is the only opposing force that affects two docking space stations.

20
Q

Properties of energy

A
• is conserved
• cannot be created or destroyed
• can change form
• measured in joules
21
Q

Work

A

Product of a net force on an object and the distance through which the object is moved.

22
Q

Power

A

Rate at which work is done.

23
Q

Power equation

A

(work done)/(time interval)

Measured in watts.

24
Q

Mechanical energy

A

Energy due to the position or the movement of something. Kinetic and potential energy

25
Q

Potential energy

A

(PE). In stored state it has the potential for doing work. Three examples: elastic potential, chemical, and gravitational potential.

26
Q

Kinetic energy

A

energy of motion. Not moving: zero units of energy.

27
Q

Energy

A

Property of an object on system that enables it to do work. Measured in joules

28
Q

Work is done when…

A

a force acts on an object that results in the object moving in direction of the force.

29
Q

Work equation

A
```work = net force * distance
W = Fd```
30
Q

1 joule =

A

1N/1m

31
Q

Gravitational potential energy

A

gravitational potential energy = weight * height

PE = mg * h

32
Q

Kinetic energy equation

A

kinetic energy = (1/2)mass * speed^2
KE = (1/2)mv^2
net force * distance = KE
Fd = (1/2)mv^2

33
Q

Work-energy theorem

A

work = (change in)KE. Whenever work is done, energy changes

34
Q

Law of conservation of energy

A

States that energy cannot be created or destroyed. It can be transformed from one form into another, but the total amount of energy never changes.

35
Q

Machine

A

Device used to multiply forces or simply change the direction of forces.

36
Q

Machine function

A

Transfers energy from one place to another or transforms it from one form to another.

37
Q

Lever

A

work input = work output
(force*distance)input = (force * distance)output

38
Q

A

(ratio output force)/(ratio input force)

39
Q

Pulley

A

Kind of lever that can be used to maintain the direction of force or change the direction of a force. can also multiply the force involved, but the amount of work done stays the same.

40
Q

In any machine…

A

…some energy is transformed into atomic or molecular kinetic energy - making the machine warmer.

41
Q

Efficiency of a machine

A

efficiency = (useful work output)/(total work input)

42
Q

Efficiency percentage

A

43
Q

Energy for life

A

there is more energy stored in the molecules in food than there is in the reaction products after food is metabolized. This energy difference sustains life.

44
Q

Fuel Cell

A

When one makes electrolysis process run backwards.

45
Q

1MW =

A

1,000,000W

46
Q

1 unit horsepower =

A

0.75kW

47
Q

What happens when simple lever rocks about its fulcrum, or a pulley turns about its axis?

A

A small fraction of input energy is converted into thermal energy.

48
Q

two ways to calculate gravitational potential energy?

A

Weight times height or mass times acceleration due to gravity (g) times height are the two ways to calculate gravitational potential energy.

49
Q

Why can wind be considered a type of solar power?

A

Wind is caused by unequal warming of Earth’s surface.

50
Q

If momentum is changing but mass remains the same, then…

A

…velocity must be changing.

51
Q

If velocity is changing then…

A

…the object is accelerating.

52
Q

Acceleration always means that…

A

…there is a net force.