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Physics Paper 2 > Forces > Flashcards

Forces Flashcards

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1
Q

What do vector quantities have? Examples?

A
  • have a MAGNITUDE and DIRECTION

- force, velocity, acceleration, displacement, momentum

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2
Q

What do scalar qualities have? Examples?

A
  • MAGNITUDE

- speed, distance, mass, temperature, time

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3
Q

What is a contact force?

A

When two objects have to be touching for a force to act

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4
Q

What is a non contact force?

A

When objects do not need to be touching to cause a force

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5
Q

How do you calculate the weight?

A

Weight= mass (kg) X gfs (N/kg)

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6
Q

What forces act on a car?

A

^ normal contact force
> driving force
< friction
!weight

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7
Q

How do you calculate work done?

A

Work done= force (N) X distance (m)

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8
Q

How do you calculate the elastic potential energy?

A

=0.5 x spring constant (N/m) x extension (m)

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9
Q

How do you calculate the moment of a force?

A

Moment = force X distance

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10
Q

How do you calculate pressure?

A

Pressure (Pa) = Force / Area (m2)

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11
Q

What does a lever do?

A

They increase the distance from the pivot at which the force is applied. This means less force is needed to get the same moment

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12
Q

What do gears do?

A

Different sized gears can be used to change the moment of a force

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13
Q

What does Newton’s first law of motion state?

A

Objects with balanced forces acting on them will stay at rest or in constant motion

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14
Q

What does Newton’s second law of motion state?

A

When an unbalanced force acts on an object, the direction of the objects acceleration is the same as the unbalanced forces direction.

F=mass x acceleration

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15
Q

What is friction?

A

A force that opposes motion when two objects slide past each other.

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16
Q

Why would a person weigh less on the moon?

A

Because the gravitational field strength of the moon is a lot smaller than that of earth. But our mass would stay the SAME

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17
Q

What does Newton’s third law state?

A

The size of the forces acting on the first object equals that of the second object. In every interaction, there is a pair of forces acting on the two objects

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18
Q

How do you convert from Nm to joules?

A

1 joule = 1 Nm

Eg 5J = 5Nm

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19
Q

What happens when you apply a force to an object?

A

It will stretch, compress or bend

20
Q

What happens when a spring is stretched or compressed?

A

Work is done which causes energy to be transferred to the elastic potential energy store of the object which is equal to the work done

If it is elastically deformed then ALL of this energy has been transferred to its epe store

21
Q

How do you calculate the force of an object?

A

Force =Spring constant X extension

22
Q

How do you investigate the relationship between the force and extension of springs? (PRACTICAL)

A

Measure the length of the Spring with a ruler when a weight is added. Continue this using more weights each time by hanging them.

23
Q

How do you calculate the moment?

A

Moment (Nm) = force X distance

24
Q

What is the moment?

A

The turning effect of a force (causes object to rotate)

25
Q

What is the pressure of a fluid?

A

A force is exerted normal to any surface in contact with the fluid

P= f/a

26
Q

What does it mean if a liquid is dense?

A

It means it has more particles in a certain space. Density is a measure of ‘compactness’ of a substance.

Density (kg/m3) =mass / volume

27
Q

What is upthrust?

A

Force that determines whether an object will sink or float. It is a resultant force. An object will float if it’s weight = upthrust.

28
Q

What is atmospheric pressure?

A

The pressure exerted by the air around us. It is created on a surface by air molecules colliding with the surface

29
Q

What happens as the altitude (height above Earth) increases?

A

The atmospheric pressure will decrease because the atmosphere becomes less dense so there are fewer air molecules able to collide with surface

Which is why cliffs have a low atmospheric pressure

30
Q

How to work out pressure in a liquid?

A

Pressure (pa) = height X gfs X density of liquid

31
Q

What is velocity?

A

It is the speed in a GIVEN DIRECTION. It is a vector quality.

32
Q

How do you calculate the speed of an object?

A

Speed (m/s) = distance (m) / time (s)

33
Q

What is acceleration? Equation?

A

It is the rate of change of the velocity. It is the change in velocity in an amount of time.

Acceleration (m/s2) = v-u (m/s) / time (s)

34
Q

What does a distance time graph show us?

A

-gradient=speed
-flat sections=object stationary
-straight sections=steady constant speed
-levelling off=slowing down
If object is accelerating, find the gradient of tangent to the curve at that point it’s speed has changed

35
Q

What does a velocity time graph show us?

A

How an objects velocity changes on a journey.

  • gradient=acceleration
  • flat sections=steady speed
  • steeper the graph=greater acceleration/deceleration
  • area under sections of graph equal to distance traveled in that time
36
Q

What is drag? How can it be avoided?

A

Resistance you get in a fluid (gas or liquid) air resistance is a type of drag. Drag increases as the speed increases.

Can be reduced by keeping shape of object streamlined eg train

37
Q

What does it mean if an object is in equilibrium?

A

It’s weight is equal to the normal contact force.

38
Q

What is the stopping distance?

A

The sum of the thinking distance and the breaking distance. It is the distance it takes to stop a car.

Stopping distance = thinking distance + breaking
distance

39
Q

What is the thinking distance? What affects this?

A

How far the car travels during the drivers reaction time. It is affected by:

  • speed
  • your reaction time- tiredness, drugs, alcohol, distractions
40
Q

What is your reaction time? What affects it?

A

The distance taken to stop once the brakes are applied. It is affected by:

  • speed
  • road surfaces/weather
  • condition of tyres
  • condition of brakes
41
Q

What happens when the brakes of a car are applied? Hazards?

A
  • brake pads pushed onto wheels which cause friction which causes work to be done
  • the work done between wheels and brakes transfers energy from kinetic energy stores to thermal energy stores

A larger braking force means a larger which can be dangerous as brakes could overheat or car could skid

42
Q

What is another equation for momentum? (Kg m/s)

A

Momentum (kg m/s) = mass (kg) x velocity (m/s)

43
Q

What does the conservation of momentum state?

A

In a closed system, the momentum before an event is the same after the event.
Eg if momentum before was 0, it would be 0 after

44
Q

What is ‘uniform acceleration’ ?

A

When the acceleration is constant.

45
Q

What is inertia?

A

The resistance an object has to a change in its state of motion

46
Q

What are some safety features of a car?

A
  • airbags reduce forces on head
  • crumple zones absorbs crash energy and reduces force
  • headrests
  • braking systems
  • seat belts increase time taken for body’s momentum to reach zero

Physics Paper 2 (4 decks)

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