Physics : Motion and Forces Flashcards

1
Q

What do vectors have?

A

Magnitude (size) and Direction

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2
Q

What do scalars have?

A

Magnitude (size) but not Direction

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3
Q

Distance is an example of what quantity?

A

Distance is a scalar quantity

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4
Q

Speed and velocity both show what?

A

Both show how fast you are going

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4
Q

Displacement is an example of what quantity?

A

Displacement is a vector quantity

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5
Q

Acceleration shows what?

A

It shows how quickly you are speeding up

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6
Q

What does uniform acceleration mean?

A

It means constant acceleration

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7
Q

Name 3 examples of vector quantities:

A

Force, velocity, displacement, weight, acceleration and momentum

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8
Q

Name 3 examples of scalar quantities:

A

Speed, distance, mass, energy, temperature and time

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9
Q

What is displacement?

A

Displacement measures the distance and direction in a straight line from an object’s starting point to it’s finishing point.

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10
Q

What is the equation that links speed, distance and time?

A

Distance travelled (m) = average speed (m/s) x time (s)

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11
Q

What is the typical walking speed?

A

1.4 m/s

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12
Q

What is the typical running speed?

A

3 m/s

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13
Q

What is the typical cycling speed?

A

5.5 m/s

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14
Q

What is the typical speed for cars in a built-up area?

A

13 m/s

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15
Q

What is the typical speed for aeroplanes?

A

250 m/s

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16
Q

What is the typical speed for cars on a motorway?

A

31m/s

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17
Q

What is the typical speed for trains?

A

Up to 55 m/s

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18
Q

What is the typical wind speed?

A

5-20 m/s

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19
Q

What is the typical speed of sound in air?

A

340 m/s

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20
Q

What is the typical speed of ferries?

A

15 m/s

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21
Q

What is the equation that links acceleration, change in velocity and time?

A

Acceleration = change in velocity / time

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22
Q

What is the equation for constant/uniform acceleration?

A

v2 - u2 = 2as

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23
Q

What do distance/time graphs show?

A

They show how far something has travelled

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24
Q

How do you find the speed from a distance/time graph?

A

The gradient is equal to the speed, so change in y over change in x

25
Q

What do velocity/time graphs show?

A

They show acceleration

26
Q

What does the gradient on a velocity/time graph represent?

A

The acceleration

27
Q

What does a flat section represent on a velocity/time graph?

A

A steady speed

28
Q

What do the uphill sections (/) on a velocity/time graph represent?

A

They represent acceleration

29
Q

What doe the downhill sections () on a velocity/time graph represent?

A

They represent deceleration

30
Q

How do you work out the distance travelled on a velocity/time graph?

A

The area under the curve is the distance

31
Q

What is needed to change motion?

A

A force

32
Q

What is Newton’s First Law?

stationary and moving

A

If the resultant force on a stationary object is zero, the object will remain stationary. If the resultant force on a moving object is zero, it will carry on moving at the same velocity

33
Q

What is acceleration directly proportional to?

A

The resultant force

34
Q

What is the equation that links force, mass and acceleration?

A

Force = mass x acceleration

35
Q

Are weight and mass the same thing?

A

No

36
Q

What is weight?

A

Weight is the force acting on a object due to gravity

37
Q

Is weight a vector or scalar quantity?

A

Weight is a vector

38
Q

What is the equation that links weight, mass and gravity?

A

Weight (N) = mass (kg) x gravity (N/kg)

39
Q

What is centripetal force?

A

A force that keeps something moving in a circle

40
Q

What is inertia?

A

The tendency to keep moving with the same velocity

41
Q

What does an objects’ inertia mass measure?

A

It measures how difficult it is to change the velocity of an object

42
Q

How can you calculate the inertia mass?

A

Use Newton’s Second Law :
m = F/a

43
Q

What is Newton’s Third Law?

A

When two objects interact, the forces they exert on each other are equal and opposite.

44
Q

What is momentum?

A

It is the product of the object’s mass and velocity

45
Q

How do you calculate momentum?

A

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

46
Q

Is momentum a vector or scalar quantity?

A

It is a vector quantity - it has size and direction

47
Q

What happens to the momentum when the mass or velocity of an object increases?

A

The momentum also increases

48
Q

What happens to the total momentum before and after an event in a closed system?

A

The total momentum before and after an event stays the same

49
Q

What is it called when the total momentum before and after an event stays the same?

A

Conservation of momentum

50
Q

What can force do to momentum?

A

Force can cause changes in momentum

51
Q

What happens when a resultant force acts on an object?

A

It causes a change in momentum

52
Q

What is the equation that links force, change in momentum and time?

A

Force (N) = change in momentum (kg m/s) / time (s)
F = (mv-mu)/t

53
Q

If the change in momentum gets faster, what happens to the force?

A

The force gets bigger

54
Q

What is the thinking distance?

A

The distance the car travels in the driver’s reaction time

54
Q

What is stopping distance?

A

It is the thinking distance + the braking distance

55
Q

What affects the thinking distance?

A

Reaction time - distance is increased by tiredness, alcohol, drugs and distractions
Speed - faster you’re going the further you will travel during your reaction time

56
Q

What is the braking distance?

A

The distance taken to stop once the brakes have been applied

57
Q

What affects the stopping distance?

A

Speed - the faster you’re going the longer it takes to stop
Mass of car - car full of people won’t stop as quickly as an empty one
Condition of brakes - worn or faulty ones won’t brake with as much force
Friction between tyres and road - if the tyre tread is worn or there is dirty/icy/wet conditions then you are likely to skid

58
Q

What is the equation that measures the energy transfer from the car to it’s brakes?

A

Energy in car’s kinetic energy store = work done by brakes
0.5 x m x v^2 = F x d