Forces Flashcards

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1
Q

acceleration

A

rate of change of velocity

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2
Q

what does the gradient on a distance time graph show?

A

velocity

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3
Q

what does the gradient and area on a velocity time graph represent?

A

area- distance travelled
gradient- acceleration

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4
Q

what forces are acting on an object in freefall?

A

only g

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5
Q

stopping distance

A

total distance travelled from when the driver first sees a reason to stop to when the vehicle stops

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6
Q

stopping distance equation

A

thinking distance + breaking distance

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7
Q

thinking distance

A

distance travelled between the moment of realizing to brake and when the breaks are applied

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8
Q

thinking distance equation

A

speed x reaction time

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9
Q

braking distance

A

distance travelled from the moment the break is used and the car comes to a stop

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10
Q

what are the 4 most common forces on an object?

A

weight
normal contact force
tension
friction

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11
Q

inertia

A

an object’s resistance to a change in velocity
(momentum/velocity)

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12
Q

friction

A

a force that opposes motion

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13
Q

what are the two types of friction?

A

contact friction
fluid friction

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14
Q

mass

A

the amount of matter an object has

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15
Q

force

A

the rate of change of momentum
(F=ma)

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16
Q

Centre of gravity

A

the point at which the weight of the object may be considered to act

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17
Q

how do you find the centre of gravity of an object?

A

when applying a force to an object t not at the center of gravity it will rotate
whereas when pushed at its centre of gravity it will be pushed

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18
Q

what is the net force of an object when in equilibrium?

A

0

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19
Q

fluid

A

any substance that flows (eg water,air)

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20
Q

what does the magnitude of drag depend on?

A

speed of the object
cross sectional area of the object
roughness of the object
density of the fluid

(drag force ∝ speed squared)

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21
Q

terminal velocity

A

when the drag force on the object is equal and opposite to its weight (acceleration)

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22
Q

the moment of a force

A

the turning effect of a force about some axis or point

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23
Q

what is the principle of moments?

A

the sum of the clockwise moments is equal to the sum of the anticlockwise moments

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24
Q

couples

A

pair of forces working in opposite directions but not in equilibrium
(they are equal and opposite and they rotate but cause no translation)

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25
Q

torque

A

the moment of a couple

26
Q

density

A

how much mass per unit volume

27
Q

what is the air pressure at sea level?

A

100,000 pa

28
Q

Archimedes principle

A

the upthrust exerted on a body immersed in a fluid is equal to the weight of the fluid that the body displaces

29
Q

work done

A

force x distance moved in the direction of the force

30
Q

energy

A

the capacity to do work

31
Q

what is the principle of energy?

A

total energy for a closed system remains constant
energy cannot be created or destroyed
energy is transferred from one store to another

32
Q

what does potential mean in physics?

A

hidden or stored

33
Q

kinetic energy

A

energy associated with an object as a result of its motion
(KE=1/2 m (v squared)

34
Q

gravitational potential energy

A

capacity for doing work as a result of an objects position in a gravitational field
(GPE=mgh)

35
Q

power

A

the rate of work done

36
Q

chemical energy

A

energy contained within the chemical bonds between atoms

37
Q

elastic potential energy

A

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

38
Q

electrical potential difference

A

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

39
Q

nuclear energy

A

energy within the nuclei of atoms

40
Q

EM energy

A

energy associated with EM waves stored within oscillating electric and magnetic fields

41
Q

sound energy

A

energy of mechanical waves due to the movement of atoms

42
Q

thermal energy

A

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

43
Q

tensile forces

A

a force that produces an extension

44
Q

compressive forces

A

a force that shortens (compresses) an object

45
Q

elastic deformation

A

the object will go to the original shape when the force is removed

46
Q

plastic deformation

A

when the object has been stretched past its elastic limit and does not go back to its original shape

47
Q

Hooke’s law

A

the extension of a spring is directly proportional to the force applied

48
Q

what are the 3 forms of loading in alevel physics?

A

compression
tension
bending

49
Q

how much an object can extend depends on what factors?

A

length
material
tension in wire
diameter

50
Q

tensile stress

A

the force applied per unit cross sectional area of the wire
(It’s essentially pressure)

51
Q

stress

A

an internal force induced in a metal in response to an externally applied force

52
Q

tensile strain

A

the fractional change in the original length of a wire

53
Q

necking

A

the point where a material starts to break

54
Q

young’s modulus

A

the ratio of stress to strain of a particular material

55
Q

newton’s first law

A

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

56
Q

newtons second law

A

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

57
Q

newton’s third law

A

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

58
Q

momentum

A

property of a moving object defined as the product of its mass and velocity

59
Q

conservation of momentum

A

total amount of momentum before is equal to the momentum after the collision

60
Q

what is a perfectly elastic collision?

A

a Collison where momentum, total energy and total KE are conserved

61
Q

what is a inelastic collision?

A

a collision where only momentum and total energy is conserved but KE isnt

62
Q

impulse

A

Change in momentum

product of force and time for which this force acts on an object
impulse of a force= change in momentum
F x change in t = change in P