Forces and Motion Flashcards

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1
Q

Speed definition and equation

A

distance travelled
time taken
Speed is defined as the rate of change of displacement

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2
Q

What is instantaneous speed

A

Speed of the car over a very short interval of time

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3
Q

What is acceleration

A

Acceleration of an object is defined as the rate of the change of velocity

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4
Q

Acceleration=

A

change in velocity

time taken

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5
Q

In a Distance time graph what does the gradient represent

A

Speed

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6
Q

In a displacement time graph what does the gradient represent

A

Velocity

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7
Q

In a velocity time graph what does the gradient and area under the graph represent

A

Acceleration and displacement

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8
Q

What are the 5 SUVAT equations

A

v=u+at, s=vt-0.5at2, s=ut + 0.5at2, s=0..5(u+v)t, v2=u2+2as

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9
Q

What is thinking distance

A

The distance travelled between the moment when you first see a reason to stop to the moment when you use the brake.
Speed x reaction time

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10
Q

Braking distance

A

The distance travelled from the time the brake is applied until the vehicle stops

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11
Q

g=

A

The acceleration of free fall =a 9.81ms-2

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12
Q

When is an object said to be in free fall

A

When an object is accelerating under gravity with no other force acting on it

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13
Q

What is terminal velocity

A

When the object has zero acceleration and the speed is constant

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14
Q

Factors affecting reaction time

A

Tiredness, drugs and alcohol, distractions

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15
Q

Factors affecting braking distance

A

Adverse road and weather conditions (wet or icy), poor vehicle conditions (brakes or tyres)

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16
Q

What is a projectile

A

A projectile is an object that is thrown at an angle to the horizontal and therefore moves in both the horizontal and vertical planes

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17
Q

Conditions in projectiles (4)

A

Constant velocity in one direction
Constant acceleration in perpendicular direction
Vertical and horizontal motion are independent of each other
No air resistance

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18
Q

Force equation when mass is constant

A

F=ma

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19
Q

Weight equation

A

W=mg

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20
Q

Unit of force

A

Newton (N) kgms^-2

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21
Q

Weight

A

The gravitational force acting on an object through its centre of mass

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22
Q

Friction

A

The force that arises when two surfaces rub against each other

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23
Q

Drag

A

the resistive force on an object travelling through a fluid

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24
Q

Tension

A

the force within a stretched cable or rope

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25
Q

Upthrust

A

An upward buoyancy force acting on an object when it is in a fluid

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26
Q

Normal contact force

A

A force arising when one object rests against another

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27
Q

Centre of mass

A

A point through which any externally applied force produces straight line motion but no rotation

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28
Q

Centre of gravity

A

An imaginary point at which the entire weight of an object appears to act

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29
Q

Factors affecting drag for an object travelling through air

A

Speed of object, shape of object, cross sectional area, roughness or texture of object, density of fluid

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30
Q

Newtons 1st law of motion

A

An object will remain at rest or continue to move with constant velocity unless acted upon by a resultant force

31
Q

Newton’s 2nd law of motion

A

The net (resultant) force acting on an object is directly proportional to the rate of change of its momentum and is in the same direction

32
Q

Newton’s 3rd law of motion

A

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

33
Q

force equation when mass is not constant

A

Change in momentum

Change in time

34
Q

Linear momentum equation

A

momentum = mass x velocity

35
Q

Impulse of a force

A

Force x change in time

Is equal to the area under a force-time graph

36
Q

Principle of conservation of momentum

A

When objects collide the total momentum before and after the collision is the same
For a system of interacting objects the total momentum in a specific direction remains constant as long as no external forces act on the system

37
Q

4 fundamental forces

A

Gravitational force, electromagnetic force, strong nuclear force, weak nuclear force

38
Q

Density definition and equation

A

The density of a substance is defined as its mass per unit volume
Density = mass
Volume

39
Q

Pressure definition and equation

A

Pressure is the normal force exerted per unit cross sectional area
Normal force
Cross sectional area

40
Q

Unit of pressure

A

Pascal is the unit of pressure where 1Pa=1Nm^-2

41
Q

Archimedes principle

A

The upthrust exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces

42
Q

Pressure in a fluid equation

A

Height x density x acceleration of free fall

43
Q

Moment of a force

A

The moment of a force is the turning effect of a force about some axis or point

44
Q

Principle of moments

A

For a body in rotational equilibrium, the sum of the anti-clockwise moments about any point is equal to the sum of the clockwise moments about the same point

45
Q

Moment equation

A

Force x distance (perpendicular distance of the line of action of a force from the axis or point of rotation)

46
Q

Couples

A

A pair of equal and opposite forces acting on a body but on different lines of action

47
Q

Torque

A

The moment of a couple

48
Q

The principle of conservation of energy

A

This states that the total energy of a closed system remains constant: energy can never be created or destroyed, but it can be transferred from one form to another

49
Q

Energy definition

A

The capacity for doing work

50
Q

Kinetic energy equation and definition

A

0.5 x mass x speed^2

Energy due to motion of an object with mass

51
Q

Gravitational potential energy equation and definition

A

Mass x change in height x acceleration of free fall

Energy of an object due to its position in a gravitational field

52
Q

Work done

A

Force x distance

53
Q

Chemical energy

A

Energy contained within the chemical bonds between atoms- it can be released when the atoms are rearranged

54
Q

Elastic potential energy

A

Energy stored in an object as a result of reversible change in its shape

55
Q

Electrical potential energy

A

Energy of electrical charges due to their position in an electric field

56
Q

Nuclear energy

A

Energy within the nuclei of atoms it can be released when the particles within the nucleus are rearranged

57
Q

Radiant/electromagnetic energy

A

Energy associated with all electromagnetic waves stored within the oscillating electric and magnetic fields

58
Q

Sound energy

A

Energy of mechanical waves due to the movement of the atoms

59
Q

Internal (heat or thermal energy)

A

The sum of the random potential and kinetic energies of atoms in a system

60
Q

Power definition and equations

A

Power is the rate of work done or rate of energy transfer
Work done
Time
Constant force x speed

61
Q

Efficiency

A

Useful output energy x 100%

Total input energy

62
Q

Tensile deformation

A

This is when tensile forces (produce extension) are exerted causing a change in shape

63
Q

Compressive deformation

A

This is when compressive forces (shorten the length of an object) are exerted causing a change in shape

64
Q

Extension

A

This is the increase in length of an object when a tensile force is exerted on it

65
Q

Compression

A

This is the decrease in length of an object when a compressive force is exerted on it

66
Q

Hooke’s law

A

The force applied is directly proportional to the extension of the spring unless the limit of proportionality is exceeded
Force applied = force constant x extension

67
Q

Tensile stress equation and definition

A

Tensile stress is defined as the force applied per unit cross sectional area of the wire.
Force
Cross sectional area

68
Q

Tensile strain equation and definition

A

Tensile strain is defined as the fractional change in the original length of the wire
Extension
Original length

69
Q

Young modulus

A

Tensile stress

Tensile strain

70
Q

Ultimate tensile strength

A

Maximum stress that a material can withstand before it breaks

71
Q

Brittle

A

This is the property of a material that does not show plastic deformation and deforms very little under high stress

72
Q

Ductile

A

This is the property of a material that has a large plastic region in the stress strain graph so can be drawn into wire.

73
Q

Tough

A

Can take lots of kinetic force

74
Q

Hard

A

Not easily scratched or dented