Physics - Forces Flashcards

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1
Q

What is a Scalar quantity

A

Scalar quantities have magnitude (size) only

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2
Q

Define vector quantity

A

Vectors have both magnitude (size) and direction

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3
Q

What is a force?

A

A push or pull

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4
Q

When are forces contact?

A

When objects are touching

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5
Q

When are forces non-contact?

A

When objects are not touching

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6
Q

Give an example of a contact force

A

Friction, air resistance, tension and normal contact force

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7
Q

Given an example of a non-contact force

A

Gravitational force, electrostatic force and magnetic force

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8
Q

What is weight?

A

The force acting on an object due to gravity.

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9
Q

What is mass?

A

The amount of matter in an object.

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10
Q

What is the equation linking weight, mass and gravitational field strength?

A

Weight = mass x gravity

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11
Q

What is used to measure weight?

A

Newtonmeter

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12
Q

Where does the weight of any object act from?

A

Centre of mass

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13
Q

What is a resultant force?

A

A single force to represent multiple forces

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14
Q

How do you calculate a resultant force?

A

Take away (opposite directions) or add (same direction) the forces.

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15
Q

When is work done on an object?

A

When a force moves it a distance.

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16
Q

What is equation linking work done, force and distance?

A

Work done = force x distance

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17
Q

How many Joules is one Newton-metre?

A

1 joule

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18
Q

What happens to the temperature of an object when work is done against friction?

A

It increases

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19
Q

What happens to an elastic object up to the limit of proportionality?

A

Elastic deformation (It is able to return to its original length)

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20
Q

What happens to an elastic object after the limit of proportionality?

A

Inelastic deformation (It will not return to its original length)

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21
Q

What is the relationship between force and extension for an elastic object?

A

Directly proportional

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22
Q

What is equation linking force, the spring

constant and extension?

A

Force = spring constant x extension

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23
Q

Is distance a scalar or vector quantity?

A

Scalar

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24
Q

Is displacement a scalar or vector quantity?

A

Vector

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25
Q

Is speed a scalar or vector quantity?

A

Scalar

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26
Q

Is velocity a scalar or vector quantity?

A

Vector

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27
Q

What is displacement?

A

Both distance and Direction

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28
Q

What is the typical value of walking speed?

A

1.5 m/s

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29
Q

What is the typical value of running speed?

A

3 m/s

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30
Q

What is the typical value of cycling speed?

A

6 m/s

31
Q

What is the equation linking distance, velocity and time?

A

distance = speed x time

32
Q

When moving in a circle at constant speed, why is velocity constantly changing?

A

Direction changes, velocity is a vector

33
Q

How do you calculate the speed of an object from a distance time graph?

A

by calculating the gradient

34
Q

How do you calculate the distance travelled from a velocity-time graph?

A

Calculate the area under the curve/line of the selected time

35
Q

How do you calculate acceleration from a velocity-time graph?

A

by calculating the gradient

36
Q

What is acceleration?

A

The change in velocity over a given period of time

37
Q

What is the equation linking acceleration, change of in velocity and time?

A

acceleration = change in velocity ÷ time

38
Q

If an object is falling due to gravity what acceleration does it have?

A

9.8 m/s 2

39
Q

What is the name for the constant speed a falling object reaches when the resistive force is equal to its weight?

A

Terminal velocity

40
Q

What does Newtons first law say?

A

The velocity of an object will only change if there is a resultant force

41
Q

Describe the motion of an object that is initially stationary, when the resultant force is zero

A

Remains stationary

42
Q

Describe the motion of an object that is initially moving, when the resultant force is zero

A

Continues to move a constant speed in the same direction

43
Q

What do we call the tendency of an object to remain in a steady state? (H)

A

Inertia

44
Q

According to Newtons second law, what is the
acceleration of an object inversely proportional to?

A

mass

45
Q

What is the equation linking force, mass and acceleration?

A

Force = mass x acceleration

46
Q

What is the inertial mass of an object? (H)

A

how difficult it is to change the velocity of an object

47
Q

What is Newtons third law?

A

When two objects interact they exert equal and opposite forces on each other

48
Q

What is stopping distance?

A

Thinking distance + braking distance

49
Q

What is thinking distance?

A

distance travelled during reaction time

50
Q

What is braking distance?

A

distance travelled once the brakes have been applied

51
Q

What is a typical reaction time?

A

0.2 to 0.9 s

52
Q

Give some factors that can affect reaction time

A

tiredness, drugs and alcohol, poor visibility

53
Q

Give some factors that can affect braking distance

A

speed, worn tyres, worn brakes, icy roads, damaged roads

54
Q

What is the law of conservation of the momentum?

A

total momentum before = total momentum after

55
Q

What is equation linking the momentum, mass and velocity?

A

momentum = mass x velocity

56
Q

Define Spring constant.

A

The stiffness of the spring

57
Q

When moving in a circle in constant speed, why is velocity constantly changing?

A

Although the speed remains constant, direction changes, and since velocity is a vector quantity velocity changes

58
Q

State Newton, second law

A

The resultant force acting on an object will cause the object to accelerate in the direction of this force

59
Q

According to Newton’s second law, what is the acceleration of an object proportional to?

A

The resultant force

60
Q

State three properties of a pair of forces which obey Newton’s third law

A

The forces are the same type, they act of two different bodies and have the same line of action

61
Q

How is the force acting on an object related to its momentum?

A

Force = rate of change of momentum

62
Q

How do safety, features such as air bags and seatbelts, reduce forces

A

Increase the time taken for the change of momentum

63
Q

What is a moment?

A

Turning affect of a force

64
Q

What is the equation linking moments, force and distance?

A

Moment of a force = force x distance

65
Q

Describe the moment when an object is balanced

A

Clockwise moment. = anticlockwise moment.

66
Q

How does a lever reduce the amount of force needed to create a moment?

A

By increasing the distance from the pivot

67
Q

What is a fluid?

A

A liquid or a gas

68
Q

What does pressure in a fluid cause?

A

A force at right angles to any surface

69
Q

What is the equation linking pressure force and area?

A

Force = pressure x area

70
Q

What is the equation, linking pressure, height, density and gravitational field strength

A

Pressure = height of the column x density of the liquid x gravitational field strength

71
Q

Describe upthrust in terms of pressure

A

Pressure on bottom surface is greater than the pressure on the top surface

72
Q

What happens to the density of the atmosphere with increasing altitude?

A

It decreases

73
Q

What creates atmospheric pressure?

A

Collisions from air molecules

74
Q

Why does atmospheric pressure decrease with high above ground?

A

Less air above as the height increases