Forces and motion definitions Flashcards

1
Q

Acceleration

A

The rate of change of velocity

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2
Q

Average speed

A

Distance over time for the entire region of interest

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3
Q

Braking distance

A

The distance travelled between the brakes being applied and the vehicle coming to a stop. It is affected by the vehicle and road conditions

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4
Q

Displacement

A

The direct distance between an object’s starting and ending positions. It is a vector quantity

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5
Q

Displacement-Time Graphs

A

Plots showing how displacement changes over a period of time. The gradient gives the velocity and curved line represent acceleration

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6
Q

Free fall

A

when the only force acting on an object is gravity

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7
Q

Instantaneous speed

A

The exact speed of an object at a specific given point

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8
Q

Projectile motion

A

The motion of an object that is fired from a point and then upon which only gravity acts

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9
Q

Reaction time

A

Time taken to process a stimulus and trigger a response to it. Affected by alcohol, drugs and tiredness

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10
Q

Stopping distance

A

The sum of thinking distance and braking distance for a driven vehicle

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11
Q

Thinking distance

A

The distance travelled in the time is takes for a driver to react

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12
Q

Velocity-Time graph

A

Plots showing how velocity changes over a period of time. The gradient gives acceleration

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13
Q

Velocity

A

The rate of change of displacement. It is a vector quantity

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14
Q

Archimedes’ principle

A

The upward force acting on an object submerged in a fluid is equal to the weight of the fluid it displaces

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15
Q

Centre of gravity

A

The single point through which the object’s weight can be said to act

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16
Q

Centre of mass

A

The point through which all the mass of an object can be said to act

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17
Q

Couple

A

Two equal and opposite parallel forces that act on an object through different lines of action. It has the effect of causing a rotation without translation

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18
Q

Density

A

The mass per unit volume of a material

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19
Q

Drag

A

The frictional force that an object experiences when it moves through a fluid

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20
Q

Equilibrium

A

For an object to be in equilibrium, both the resultant force and resultant moment acting on the object must be equal to zero

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21
Q

Free-Body diagram

A

A diagram showing all the forces acting on an object

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22
Q

Friction

A

The resistive force produced when there is relative movement between two surfaces

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23
Q

Moment of force

A

The product of a force and the perpendicular distance from the line of action of the force to the pivot

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24
Q

Newton

A

The unit of force

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25
Q

Newton’s second law

A

The sum of the forces acting on an object is equal to the rate of change of momentum of the object

26
Q

Normal contact force

A

The reaction force between an object and surface

27
Q

Pressure

A

The force that a surface experiences per unit area, measured in Pascals(Pa)

28
Q

Principle of moments

A

For an object to be in equilibrium, the sum of the clockwise moments acting about a point must be equal to the sum of the anticlockwise moments acting about the point

29
Q

Tension

A

The result of two forces acting on an object in opposite, outwards directions

30
Q

Terminal velocity

A

The maximum velocity of an object that occurs when the resistive and driving forces acting on the object are equal to each other

31
Q

Triangle of Forces

A

A method of determining the resultant force of two forces, by joining them tip to tail. The resultant force is given by the force that would complete the triangle

32
Q

Upthrust

A

The upwards force that a fluid applies on an object

33
Q

Weight

A

The product of an object’s mass and the gravitational field strength at its location

34
Q

Conservation of energy

A

In a closed system with no external forces the total energy of the system before an event is equal to the total energy of the system after the event

35
Q

Efficiency

A

The useful output (power/energy)/total input

36
Q

GPE

A

Gravitational potential energy - the energy gained by an object when it is raised by a height in a gravitational field

37
Q

Kinetic energy

A

The energy an object has due to its motion

38
Q

Power

A

The word done or energy transferred by a system divided by the time taken for that to be done

39
Q

Work done

A

The energy transferred when a force moves an object over a distance

40
Q

Brittle

A

Shows very little strain before reaching its breaking stress

41
Q

Compression

A

The result of two coplanar forces forces acting into an object. Compression usually results in a reduction in the length of the object

42
Q

Compressive deformation

A

The changing of an object’s shape due to compressive forces

43
Q

Ductile

A

It can undergo very large extensions without failure and be stretched into wires

44
Q

Elastic deformation

A

If a material deforms with elastic behaviour it will return to its original shape when the deforming forces are removed. The object will not be permanently deformed

45
Q

Extension

A

The increase of an object’s length

46
Q

Force-extension graph

A

A plot showing how an object extends as the force applied increases. For an elastic object, the gradient should be linear up to the limit of proportionality. The gradient gives the spring constant

47
Q

Hooke’s law

A

The extension of an elastic object will be directly proportional to the force applied to it up to the object’s limit of proportionality

48
Q

Plastic deformation

A

If a material deforms with plastic behaviour, it will not return to its original shape when the deforming forces are removed. The object will be permanently deformed

49
Q

Polymeric

A

A material made from polymers

50
Q

Spring constant

A

The constant of proportionality for the extension of a spring under a force. The higher the spring constant, the greater the force needed to achieve a given extension

51
Q

Strain

A

The ratio of an object’s extension to its original length. It is a ratio of two lengths and so has no unit

52
Q

Stress

A

The amount of force acting per unit area. Its unit is Pascal(Pa)

53
Q

Tensile deformation

A

The changing of an object’s shape due to tensile forces

54
Q

Ultimate tensile strength

A

The maximum stress that an object can withstand before fracture occurs

55
Q

Young Modulus

A

The ratio of stress to strain for a given material. Its unit is the Pascal (Pa)

56
Q

Conservation of momentum

A

The total momentum of a system before an event must be equal to the total momentum of the system after the event, assuming no external forces act

57
Q

Elastic collisions

A

A collision in which the total kinetic energy of the system before the collision is equal to the total kinetic energy after the collision

58
Q

Impulse

A

The change of momentum of an object when a force acts on it. It is equal to the product of the force acting on the object and length of time over which it acts

59
Q

Inelastic collisions

A

A collision in which the total kinetic energy of the system before collision is not equal to KE of system after

60
Q

Linear momentum

A

The product of an object’s mass and linear velocity

61
Q

Newton’s first law

A

An object will remain in its current state of motion unless acted on by a resultant force. An object requires a resultant force to be able to accelerate

62
Q

Newton’s third law

A

If an object exerts a force on another object, then the other object must exert a force back that is opposite in direction and equal in magnitude