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Physics > Forces and Motion > Flashcards

Forces and Motion Flashcards

0
Q

Acceleration

A

Change in velocity / time taken

a = (v - u)
____

      T
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1
Q

Average speed

A

Distance moved / time taken

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2
Q

Scalar quantities

A

A quantity with magnitude (size) but no specific direction

• e.g (energy, mass)

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3
Q

Vector quantities

A

A quantity that has both magnitude (size) and direction.

• e.g velocity, acceleration and force.

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4
Q

Gravitational field strength

A

N/Kg

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5
Q

Momentum

A

Kg m/s

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6
Q

Distance-time graphs

A
  • gradient or slope gives speed
  • straight lines mean constant speed

Gradient = distance/time

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7
Q

How to measure speed of cars

A
  1. Measure the distance between two points along a straight section of he road with a tape measure or click wheel.
  2. Use a stopwatch to measure the time taken for a car to travel the measured distance
  3. Use speed = distance/time to solve.
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8
Q

Displacement =

A

Distance travelled in a particular direction.

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9
Q

Velocity

A

Speed in a particular direction

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10
Q

Converting speed from m/s to km/h

A

To convert m/s to km/h • multiply by 3.6

• e.g (12.8 m/s x 3.6 = 46.1 km/h)

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11
Q

Velocity-time graphs

A
  • gradient gives ACCELERATION
  • straight lines means constant acceleration
  • horizontal line = constant speed.
  • area under graph = distance travelled
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12
Q

Forces

A

Forces are pushes or pulls that one body exerts on another.

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13
Q

Weight (gravitational force)

A

The force that acts on a body because of gravity

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14
Q

Friction

A

The force that opposes motion (either when you try to make something move or whilst its moving)

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15
Q

Air resistance (drag)

A

Friction between an object and the air (or gas) that it is moving through.

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16
Q

Viscous drag

A

Similar to air resistance but occurs when an object is moving through a liquid. Drag force in liquids.

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17
Q

Upthrust

A

The upward force that liquids and gases exert on objects.

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18
Q

Magnetic force

A

Forces that magnets exert on other magnets or things made of iron (or other ferrous materials).

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19
Q

Electrostatic force

A

The force between electrically charged particles.

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20
Q

Normal reaction

A

The special name for the contact force that acts on an object pressing down on another object.

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21
Q

Tension

A

In strings, cables, ropes etc. that are being stretched (not slack)

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22
Q

Unbalanced forces on an object cause it to change the way it is moving:

A
  • it will accelerate
  • it will decelerate
  • change the direction in which it is moving
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23
Q

Resilient/elastic materials

A

Do not break easily and tend to return to original shape when the forces acting on them (which cause a deformation) are removed.

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24
Q

Hooke’s law

A

Increase in length (extension) of a spring is directly proportional to the force pulling on it.

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25
Q

Elastic limit

A

The limit at which a spring changes shape permanently and does not return to its original length.

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26
Q

Rubber bands and Hooke’s law

A

Rubber bands do not obey Hooke’s law. The extension is not directly proportional to the force causing it.

27
Q

Experiment for friction. Different factors:

A
  • the contact force (normal reaction) between the 2 surfaces
  • the area of the surfaces in contact
  • the type of surfaces in contact - the block could be pulled first on a rough surface then on a smooth surface.
28
Q

Force equation

A

Force = mass x acceleration

29
Q

Friction advantages

A

Can help make tyres that grip the road better and to make effective brakes.

Useful for parachuting. Fluid friction is very desirable.

30
Q

Friction disadvantages

A

Reducing friction means that machines can work more efficiently (wasting less energy) and do not wear out quickly.

Special fabrics used in swimming and cycling to reduce the effects of fluid friction to achieve faster times in races.

31
Q

How does force link with acceleration?

A

• GIVEN THAT THE MASS IS CONSTANT

Acceleration of an object is proportional to the force acting on it. (double the force = double the acceleration)

32
Q

For a given force…

A

The bigger the mass of an object the smaller the rate of acceleration.

33
Q

What factors can reduce the maximum braking force you can apply without skidding?

A
  • poor tyres
  • water
  • oil
  • ice
34
Q

Stopping distance is…

A

The sum of the thinking distance and braking distance

35
Q

Thinking distance

A

The distance you travel before applying brakes

36
Q

Braking distance

A

The distance you travel while the car is decelerating to rest

37
Q

Factors affecting thinking distance:

A
  1. Depends on person driving car.
  2. Whether driver is tired or under the influence of alcohol or drugs.
  3. Poor visibility
38
Q

Factors affecting braking distance:

A
  1. Poor road conditions (water, ice, oil?)
  2. Skidding/over-braking
  3. Poor car tyres or brakes
39
Q

Weight

A

The force that acts on an object because of gravity

40
Q

Weight equation

A

Weight = mass x gravitational field strength

W = m x g

41
Q

Drag coefficient

A

Measure of how easily an object moves through the air.

Cars have low “drag coefficient”.

Streamlined, smooth surfaces produce less drag.

42
Q

Momentum

A

Measure of how difficult it is to stop something that is moving.

43
Q

Momentum equation =

A

Momentum = mass x velocity

(In kg m/s) (In kg) (In m/s)

44
Q

Newton’s second law

A

Rate of change of momentum of an object is proportional to the size of force acting on it.

45
Q

Conservation of momentum

A

Total momentum of two bodies before collision = total momentum of two bodies after collision

46
Q

Elastic collision

A

Collision where no energy is lost

E.g collisions between molecules in a gas are taken as perfectly elastic.

47
Q

Partially elastic collisions

A

Collisions in which some of the kinetic energy is lost as it is converted into sound and heat.

48
Q

Inelastic collisions

A

When colliding objects do not rebound. They stick together.

49
Q

Centre of gravity in a symmetrical sheet of card can be found…

A

At the point where the axes of symmetry cross.

50
Q

What factors can reduce the maximum braking force you can apply without skidding?

A
  • poor tyres
  • water
  • oil
  • ice
51
Q

Stopping distance is…

A

The sum of the thinking distance and braking distance

52
Q

Thinking distance

A

The distance you travel before applying brakes

53
Q

Braking distance

A

The distance you travel while the car is decelerating to rest

54
Q

Factors affecting thinking distance:

A
  1. Depends on person driving car.
  2. Whether driver is tired or under the influence of alcohol or drugs.
  3. Poor visibility
55
Q

Factors affecting braking distance:

A
  1. Poor road conditions (water, ice, oil?)
  2. Skidding/over-braking
  3. Poor car tyres or brakes
56
Q

Weight

A

The force that acts on an object because of gravity

57
Q

Weight equation

A

Weight = mass x gravitational field strength

W = m x g

58
Q

Drag coefficient

A

Measure of how easily an object moves through the air.

Cars have low “drag coefficient”.

Streamlined, smooth surfaces produce less drag.

59
Q

Momentum

A

Measure of how difficult it is to stop something that is moving.

60
Q

Momentum equation =

A

Momentum = mass x velocity

(In kg m/s) (In kg) (In m/s)

61
Q

Newton’s second law

A

Rate of change of momentum of an object is proportional to the size of force acting on it.

62
Q

Conservation of momentum

A

Total momentum of two bodies before collision = total momentum of two bodies after collision

63
Q

Elastic collision

A

Collision where no energy is lost

E.g collisions between molecules in a gas are taken as perfectly elastic.

64
Q

Partially elastic collisions

A

Collisions in which some of the kinetic energy is lost as it is converted into sound and heat.

65
Q

Inelastic collisions

A

When colliding objects do not rebound. They stick together.

66
Q

Centre of gravity in a symmetrical sheet of card can be found…

A

At the point where the axes of symmetry cross.

Physics (4 decks)

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