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Motion, Forces & Energy Flashcards

1
Q

Describe Energy efficiency

A

Percentage of useful energy transferred

No energy in the real world is 100% efficient

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2
Q

What is the formula for (energy) efficiency?

A

Efficiency (%) = (Useful energy/Total energy) x 100

Applicable to energy transfers and power

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3
Q

What is a Sankey Diagram?

What does a Sankey Diagram show?

A

A diagram showing transfers of energy while also showing how much energy is transfered to different places.

Looks like an arrow that splits into other arrows

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4
Q

Would a light bulb produce more, equal or less energy than the initial input?

A

Less
Because no energy transfer is 100% efficient, some energy has to be lost on the way

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5
Q

Def. pressure

A

A measure of force per Area

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6
Q

What is the formula for pressure?

A

P = F/A
P = Pressure (Pa)
F = Force (N)
A = Area (m2)

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7
Q

What does SI stand for?

A

System internationale

The accepted system to use for physics

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8
Q

What is the unit uses for N/m2

A

Pascals (Pa)

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9
Q

What is 100 cm2 converted to metres?

A

0.01m2

Divide by 1002

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10
Q

Why will a small object and a large object experience the same pressure at the bottom of lake?

A

Because pressure is per volume already, so the formula takes that into account.

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11
Q

What is the formula for pressure in liquids

A

P = ρgΔh
P = Pressure (Pa)
p = Density (kg/m^3)
g = Gravitational field strength (9.8m/s2)
Δh = Change in depth (m)

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12
Q

What is the formula for moments

A

τ = Fd

τ = moments (nm)
F = Force (N)
d = distance (m) (from pivot)

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13
Q

How do you find center of mass if object is irregular

A

Object must be hung at different points and a vertical line directly drawn.
The intersection of those lines shows center of gravity.

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14
Q

How do you find the center of mass in a regular object

A

Find geometrical center

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15
Q

Define center of mass/ gravity

A

The point where gravity or weight appears to act through

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16
Q

What do we know about momentum?

A

Always conserved
Vector

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17
Q

What is the formula for momentum

A

p = mv

p = momentum (kg m/s)
m = mass (kg)
v =velocity (m/s)

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18
Q

Define momentum

A

this def is a bit wonky, …

The amount of ‘oumph’ an object has, or better :
The amount of force required to stop the movement of an object

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19
Q

What are elastic collisions

A

Kinetic energy and momentum conserved

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20
Q

What are inelastic collisions

A

Kinetic energy and momentum not conserved,
due to energy loss in other forms
e.g. heat and sound

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21
Q

What equation can we create using
p = mv
To solve a problem with two moving objects that stick together, based on the fact that momentum is conserved (elastic momentum)

A

before collision (A, B) After collision (AB)

pA + pB = pAB

mA vA + mB vB = m AB v AB

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22
Q

Explain momentum conservation

A

If momentum is conserved, means
total momentum before collision = total momentum after collision

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23
Q

Def: mass

A

Kg - amount of matter that makes up an object

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24
Q

Def. Weight

A

N - force on an object due to a gravitational field

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25
What is the formula for Fg ? Give names and units
mass (kg) I Fg = mg — Acceleration due to gravity (m/s^2) I Force due to gravity (N) (also weight)
26
A seesaw has a pivot which is too much in the left. In the middle of the seesaw, there is a force acting. what is it?
? is the weight of beam, pivot point The beam itself will create a turning effect because pivot is not on pivot point
27
What are 2 other ways to say 'moment'?
Torque Turning effect
28
EASER EGG! HAHA!
boy, take a break, please!
29
Equilibrium: Bob and Rob are standing on a see-saw again. They should know better. Bob: 80 kg Rob : ? kg ____________________________________________ 2.4m <-------------------> ∆ <------------>1.3 m
Fg = mg Fg = 80 x 9.8 Fg = 1881.6 Fg = T/d F = 1447.38 N + m = fg/g m = 147.69 kg OMG Rob!! no more chocolates for you!!
30
What is an equilibrium
When the turning effect on both sides of the pivot is equal
31
Def. Moments
A turning effect on an object around a pivot point
32
What is the weight force if the mass is 20kg?
see for yourself : 20 x 9.8 = 196 N
33
How do you find total distance traveled? Speed
34
How do you find total distance traveled? Speed
Vxt
35
How do you find the total distance travelled in a speed-time graph?
s = v x t Find the area of shapes then ad together to get the total area
36
What happens to velocity in circular motion
Constantly changing, always accelerating, this means it needs force to keep spinning a = ∆ v ______ ∆ t
37
Explain why objects in circular motion are always accelerating, and the direction of the velocity
As an object travels at constant speed, and it moves around a path, the direction is constantly changing. As velocity is a vector quantity, a change in direction of an object means its velocity is also changing . Due to the formula, a = ∆v/∆t, acceleration is also constantly changing. The direction of velocity is perpendicular to the centripetal force.
38
rearrange the acceleration formula to find the change in time
∆t = ∆v/a
39
In circular motion, when is a stronger force needed for a constant acceleration?
- larger mass (with constant v and r) - smaller radius ( with constant m and v)
40
What is 3km/h in m/s ?
= 3000 m / 3600s = 0,183 m/s OR = 3 divided by 3.6 = 0,83 m/s
41
What is friction Which state of matter provide friction (other than solids)
A force between 2 surfaces, may impede motion and produce heating Friction (drag) acts on objects moving through liquids, and through gases (e.g. air resistance)
42
What is the formula for Hooke's Law
K = F/ x K is Spring constant (N/m), the amount of resistance a spring has F is force (N) x is extension (n)
43
What is the other formula for K = F/x ?
F = (-)Kx F is force (N) x is extension (n) K is Spring constant (N/m) x is negative if spring is compressed
44
What is the acceleration due to earth due to gravity
9.8 m/s^2
45
What is the formula for density (+ units)
p = m/v p is density (g/ml) m is mass (g) v is volume (m^3)
46
What are the effect of stacking springs in parallel vs in series
In parallel = spring constant x2 In series = spring constant /2
47
What is this F 𝛼 X
Directly proportioned 𝛼 = proportional to K = F/x
48
With an object moving in circular motion, what are the 2 forces in action ?
Velocity and centripetal force
49
Define centripetal force
force acting inwards on a circular motion
50
When does the k = fx formula not apply?
After the limit of proportionality
51
What is the formula for force concerning circular motion?
F = mv^2 / r F = force (N) m = mass (Kg) v = velocity ( m/s) r = radius (m)
52
How would you find the average speed of the journey? (graph with distance ad time, speed is not always the same)
V = S/t S = total distance t = total time
53
How do you find acceleration on a speed -time graph?
a = ∆V/ ∆t ∆V = Y axis ∆t = X axis
54
What is Newton's 2nd law?
F = ma Force = mass x acceleration The acceleration of an object depends on the mass of object and force applied
55
What is Newton's 3rd law
For each force applied, there is a reaction of an equal and opposite force
56
What is Newton's first law
An object that is stationary will remain that way unless another force acts upon it. Same with an object that is moving.
57
Explain distance vs displacement
Distance is how far an object has travelled, a magnitude, while displacement is how far out of place an object is in a straight line and therefore a vector.
58
How do you find the volume of an irregular object
Calculate displacement of water (Eureka!)
59
What is net force ?
resultant force combination of all forces applied
60
What is the difference between v = s/t and a = ∆V/ ∆t
average speed, distance, time acceleration, change in velocity, change in time
61
1. --------------------------> Km/h m/s <------------------------- 2.
1.3.6 2.3.6
62
What are the units ? v,s, t
V = Speed (average) (m/s) or S = Distance (m) t = time (s)
63
Def. Vector
A quantity with a magnitude and a direction
64
Def. Scalar
amount e.g. 250 g
65
a car goes 9km North, 9 km East How to find angle? What is displacement What is distance traveled
trigonometry Distance from start point Distance travelled
66
Car goes 11 m/s > car goes 4 m/s What is the change in velocity?
V^f -V' = V change 4 - 11 = -7m/s
67
Easter Egg!!
get up and have a little happy dance on the spot !
68
Explain technique how to find question mark: b ￬ a → ↘︎?
Use a pythagorean theorem to find resultant force
69
What is formula for Acceleration
a = ∆V / ∆t ∆ = change in ∆ V = change in velocity ∆t = change in time Direction matters ! 0---------------> 50 > Velocity = o m/s^2 <-----------------
70
What is the unit for Acceleration?
m/s^2
71
What is deceleration
the opposite of acceleration - m/s^2
72
Which equation involves Average speed Distance and time How are they represented ?
V = s/t speed is distance dividend by time you can also represent them in a triangle : S V t
73
Def. Resultant force
10 N 5N --------> object <---------- ￬￬ 5N ----> object
74
What is the formula for kinetic energy
Ek = 1/2mv^2 Ek = Kinetic energy (J) m = mass (kg) v = speed (m/s)
75
What are the main energy transfers
- Mechanical - Electrical - Heating - electromagnetic, sound, other waves ...
76
Name 7 sources of energy production
- wind turbines - water turbines - nuclear - fuels - geothermal - solar - tidal / waves
77
Define power
The rate at which the work is done/ The rate of energy transfer
78
Def. boiler
Uses heat from the burning of fuels to boil water to steam
79
Define Turbine
Transforms energy from a fluid (liquid/gas) into rotational kinetic energy
80
Define Generator
Consist of a coil (or coils) of wire that rotate in a magnetic field to produce an electric current
81
Define kinetic energy
Energy stored in moving objects
82
Describe the energy transfers and stores 1. torch battery ---> 2. ---> 3. bulb ---> 4. ---> 5. Surroundings 3. bulb ---> 6. ---> 7. Surroundings
1. Chemical 2. Electrical 3. Thermal * 4. Thermal 5. Thermal * 6. Light 7. Thermal * * = Internal
83
How can you find the relationship between the loss of Ep---> the gain of Ek or vice versa
Energy is conserved! Etotal = Ek + Ep mg ∆ h = 1/2 mv^2 g ∆ h = 1/2 V^2 before after ----------------->
84
How can you find the relationship between the loss of Ep---> the gain of Ek or vice versa
Energy is conserved! Etotal = Ek + Ep mg ∆ h = 1/2 mv^2 g ∆ h = 1/2 V^2 before after -----------------> energy is transfered
85
What is the formula for gravitational potential
Ep = mg∆h Ep = gravitational potential (J) m = mass (kg) g = gravitational field (9.8 m/s) ∆h = Change in height (m)
86
What are the main energy stores
Kinetic Nuclear Electrostatic Thermal Magnetic Chemical potential Elastic potential Gravitational potential
87
What are the formulae for power
p = w/t or p = ∆E / t p = power (W) t = time (s) W = work (J) ∆E = change in energy (J)
88
What is power measured in ?
Watts (W) a.k.a. (J/s)
89
Define "Work"
A transfer of energy "work has been done"
90
What is the formula for work
W = Fd W = Work (J) F = Force (N) d = distance (m)
91
What are some hardy rearrangements of mg∆h = 1/2 mv^2
V = √2g∆h and ∆h = (1/2V^2)/g
92
What is the law of conservation of energy
Energy can not be created or destroyed. I can only be transferred from one store to another.
93
What is the equation for impulse
∆p = F∆t ∆p = impulse (Kg m/s) F = Force (N) ∆t = change in time (s)
94
Define impulse
A change of momentum of an object. It also describes the forces involved during the change in momentum
95
Describe nuclear E - origin - advantages/ disadvantages - transfers
EMPTY
96
Describe geothermal E

Physics (7 decks)

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