Forces and Motion Flashcards

1
Q

Units for acceleration due to gravity

A

m/s2 or N/kg

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2
Q

What is a vector quantity

A

A quantity with a magnitude and direction eg. velocity

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3
Q

What is a scalar quantity

A

A quantity that has a magnitude but no direction eg. mass

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4
Q

What is acceleration measured in?

A

m/s2

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5
Q

What is Newton’s first law?

A

An object will stay at rest or continue to move at a constant speed in the same direction unless acted upon by a resultant force

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6
Q

How do you find the resultant force of two objects?

A

Find the difference between both forces

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7
Q

What factors affect the thinking distance of a person in a car?

A

Alchohol
Poor visibility
Old age
Tiredness
Drugs

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8
Q

What factors can affect the stopping distance of a car?

A
  • Its mass
  • Its speed
  • The driver’s reaction time
  • The condition of the brakes
  • The road conditions
  • Amount of friction between the tyres and road
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9
Q

What is speed?

A

How fast an object is moving

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10
Q

What is velocity?

A

Speed in a certain direction

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11
Q

What is distance?

A

How far something has or will travel

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12
Q

What is displacement?

A

Distance in one direction as the fastest route

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13
Q

Give some examples of vector quantities

A
  • All forces (eg. Weight)
  • Velocity
  • Displacement values
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14
Q

Give some examples of scalar quantities

A
  • Energy
  • Speed
  • Mass
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15
Q

How are vector quantities shown on diagrams?

A

With arrows

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16
Q

What does a flat line mean on a distance time graph?

A

The object is stationary

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17
Q

What does a curve represent on a distance time graph?

A

Acceleration or deceleration

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18
Q

What does a straight line mean on a distance time graph?

A

Object is stationary

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19
Q

What does a flat line mean on a velocity time graph?

A

The object is travelling at a constant speed

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20
Q

What does a diagonal line mean on a velocity time graph?

A

Acceleration or deceleration

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21
Q

How do you find the distance travelled in a velocity time graph?

A

You work out the area under the graph

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22
Q

How do you work out the acceleration on a velocity time graph?

A

Use the equation

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23
Q

Describe an object’s motion if the resultant force is 0

A

Either:

  • It will be travelling at a constant speed
  • It will be stationary
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24
Q

What different resistive forces could be acting on a car when in motion?

A
  • Air resistance
  • Friction
  • Contact force
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25
Q

What is terminal velocity?

A

The maximum velocity of an object, reached when the forces moving the object are balanced by its frictional forces

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26
Q

What is thrust?

A

A force used to move something forwards or up

27
Q

What are balanced forces?

A

When the resultant force is 0

28
Q

If two forces are balanced, what is the resultant force?

A

0

29
Q

Is the moon travelling at a constant velocity?

A

No, because is not moving in a constant direction

30
Q

What is constant velocity?

A

When something is travelling at a constant speed in a constant direction

31
Q

What is the name of the force bringing something forward?

A

Driving force

32
Q

What is Newton’s second law?

A

F = ma

33
Q

What is inertial mass?

A

The ratio of force over acceleration

m = F/a

34
Q

What is Newton’s third law?

A

For every action there is an equal and opposite reaction

35
Q

What are the 4 criteria for Newton’s third law pairs?

A

The forces must be:

  • Equal in magnitude
  • Acting in the opposite direction
  • The same type of force
  • Acting on different objects
36
Q

Give an example of a Newton third law pair

A

The gravitational force of the Earth on the Moon
and
The gravitational force of the Moon on the Earth

37
Q

Stopping distance = ???

A

Thinking distance + braking distance

38
Q

What factors affect the braking distance of a car?

A
  • Its mass
  • Its speed
  • The condition of the brakes
  • The condition of the road
  • The amount of friction between the tyre and the road surface
39
Q

What factors affect a drivers reaction time (thinking distance)?

A
  • Age
  • Alcohol or drugs
  • Poor visibility
  • Tiredness
  • Distractions
40
Q

What is the equation for momentum?

A

Momentum = mass x velocity

41
Q

What are the units for momentum?

A

Kg m/s

42
Q

What is the conservation of momentum?

A

The principal that in a collision the total momentum before the event is equal to the total momentum after the event.

43
Q

How does a crumple zone help in a car crash.

A

A crumple zone will change the shape of a car during a crash. If the change in momentum happens over a longer time, there is less force, shown by the equation F = mv-mu/t

44
Q

What is the typical speed of sound?

A

330 m/s

45
Q

What is the typical cycling speed of a person?

A

6 m/s

46
Q

What is the typical running speed for a person?

A

3 m/s

47
Q

What is free fall?

A

The acceleration due to gravity

48
Q

Name 3 car safely features designed to reduce the time of a collision

A
  • Seat belts
  • Air bags
  • Crumple zones
49
Q

How do wet roads affect the stopping distance of a car?

A

Increases braking distance as wet roads reduce friction between the road and the car tyres

50
Q

What is centripetal force?

A

The resultant force of an object travelling in a circle, acting towards the centre of the circle

51
Q

Describe the relationship between the rate of change of momentum and the force

A

They are directly proportional

52
Q

How do you calculate the braking distance of a car?

A
  • Find the work done (E) to stop it
  • This is the same the kinetic energy of the car (1/2mv2)
53
Q

How do you calculate gear ratio?

A

Amount of teeth on driven gear
———————————————
Amount of teeth on driver gear

54
Q

What is a moment?

A

A turning force

55
Q

Which of these will be able to cut through tougher stuff and why:

  • Long handled scissors
  • Short handled scissors
A

The longer handled scissors, because the distance normal to the direction of the force is directly proportional to the moment

56
Q

Describe the relationship between clockwise and anticlockwise moments when an object is at equilibrium

A

The sum of clockwise moments = The sum of anti-clockwise

57
Q

Name two methods for determining the speed of an object

A

- Dropping a ball from a height of 1m and measuring the time taken
- Using light gates

58
Q

What is the typical speed of a car?

A

10-30 m/s

59
Q

What is the typical speed of a plane?

A

200-250 m/s

60
Q

What is the acceleration in free fall?

A

10 m/s2

61
Q

Describe an object’s motion if the resultant force is not 0

A

It accelerating/decelerating and/or changing direction

62
Q

What is weight?

A

The force due to gravity on an object

63
Q

Describe the relationship between the weight of an object and the gravitational field strength

A

They are directly proportional

64
Q

How does a higher speed affect the stopping distance of a car?

A

The faster the car is travelling, the larger the breaking distance