Chapter 4/5 Flashcards Preview

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Flashcards in Chapter 4/5 Deck (53):
1

objects in mechanical equilibrium are

at rest/ not moving
- have 0 acceleration

2

if there is a net force (netF = not 0) it will cause

changes in motion (direction or magnitude)

3

force

causes acceleration

4

acceleration

is directly proportional or the net force
ex. 3 X force = 3 X acceleration

5

Gravity/Weight

Fg
Force of which an objects attracts another object to itself
Fg = (m)(g) g=acceleration of gravity 9.8m/s^s
Direction: Downward (towards earth)

6

Friction

Ff
Exerted by a surface as object moves/trys to move across it
Direction: Opposite the direction of motion

7

Air Resistance

Fair
Acts upon objects as they move through air
Affected by speed and surface area
Direction: Opposite the direction of motion

8

Normal/Support

Fn
Force exerted to hold another object up
Direction: Perpendicular to surface

9

Applied

Fa
Exerted by a person or object
Direction: Direction applied

10

Tension

Ft
Transmitted through a string, rope or wire when it is pulled at each end
Direction: Pulls along direction at length

11

Spring

Fs
Exerted by a compressed or stretched spring
Direction: direction of restoring it back to original position

12

Friction is a force that

holds back the movement of a sliding object

13

Friction acts in what direction?

opposite Direction to the way an object wants to slide

14

Friction is either

static or kinetic/dynamic/sliding

15

static friction

the frictional force opposing placing a body at rest into motion

16

dynamic/kinetic/sliding friction

the frictional force tending to slow a body in motion

17

friction can occour in what states?

solid, liquid and gas

18

fluid friction

called Drag
- Drag is greater in water than in air
- Dependent on SA and speed

19

Mass

- quantity of matter in a object
- measure of inertia or sluggishness that an object exhibits in response to any effort made to change its state of motion
ex. shaking test tests mass/ how resistant it is to change/inertia

20

weight

force upon an object due to gravity

21

mass and weight are

directly proportional
ex mass X 2 = weight X 2

22

Is it eaiser or harder to accelerate a car on the moon?

same
- the mass of the car is the same because it is independent of gravity

23

mass of something on the moon compared to earth is..

the same

24

mass resists

acceleration
- the acceleration produced is inversely proportional
As mass increases, acceleration decreases

25

acceleration of an object is

- directly proportional to the net force action on the object
- its is in the direction of the net force
- inversely proportional to the mass of the object

26

formula that represents Newton's 2nd law of motion

F = (M)(A)

M = mass in kg
A = acceleration in m/s^2

kg*m/s^2 is known as a Newton (N)

27

Galileo founded what 2 concepts?
What couldnt he explain?

Inertia and acceleration (and was first to measure acceleration of falling objects)
Why objects with different masses fall with equal acceleration

28

Newtons 2nd Law

The acceleration of a object is directly proportional to the net force acting on the object
It is in the direction of the net force
And inversely proportional to the mass

29

Mathamatically Non- free fall

a= Fnet = mg-R
------ -------
m m

mg = weight
R = Air resistance

30

Air drag

- depends on two factors, speed and frontal area of the falling object

31

when the upward drag cancels out the downward acting weight,

net force is 0
acceleration ends

32

when the acceleration terminates

we say the object has reached its terminal speed/velocity

33

light woman & heavy man jump out of a plane, and open same size parachutes at the same time
Who will get to 0 acceleration first?
Who will have a faster terminal speed?

Who will get to 0 acceleration first?
Light woman (less air drag)

Who will have a faster terminal speed?
Heavy man

34

2 factors that affect friction between solids

weight and surface texture

35

a interaction is comprised of a pair of forces that are

equal in magnitude
opposite in direction

36

Newton's 3rd law of motion

whenever one object exerts a force on a second object the second object exerts an equal and opposite force on the first object

37

gravity is the force between

earth and mass on its surface

38

when do we sense gravity (in general)

when huge masses like the earth are involved

39

Gm*m ? F if you double the distance (m, m, 2d)
-------
d2

1/4 F

40

Gm*m ? F if you triple the distance (m, m, 3d)
-------
d2

1/9 F

41

Gm*m ? F if you quadruple the distance (m, m, 4d)
-------
d2

1/16 F

42

? F if you double one of the masses (2m, m, d)
Gm*m
-------
d2

2F

43

? F if you double both masses (2m, 2m, d)
Gm*m
-------
d2

4F

44

? F if you cut the distance in half (m, m, d/2)
Gm*m
-------
d2

4 F

45

? F if you double both masses and dist. (2m 2m 2d)

Gm*m
-------
d2

F

46

Hooke's law

the amount of stretch in a spring is proportional to the amount of force exerted on the spring
the distance is opposite the displacement
- slope is k (spring constant)

47

Universal gravitation

every object in the universe attracts every other object in the universe with a force that is directly proportional to the masses
and inversely proportional to the square of the distances betwen their centres

48

Non Free fall
? acceleration
? R

acceleration is less than g
R = m*g

49

Non Free Fall
-what is air resistance dependent on

surface area
speed
increases as an object picks up speed

50

Non free fall
- what happens when air resistance = weight

acceleration stops = 0
speed = terminal speed

51

Coefficient of friction
Static vs Kinetic

- between 2 solids
u(s) = static IS GREATER
u(k) = kinetic

52

Coefficient of friction
unit? shows?

shows how much resistance you're going to recieve from 2 surfaces
- no units
Ff = u(Fn)

53

Newtons first law

Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by force impressed upon it