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Physics Paper 2 > Forces > Flashcards

Forces Flashcards

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1
Q

What is a vector

A

It has magnitude and direction

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2
Q

What is a scalar

A

Only has magnitude

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3
Q

What are examples of a vector quantity

A

Displacement
Velocity
Acceleration
Pressure
Momentum

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4
Q

What are examples of scalar quantities

A

Distance
Speed
Time
Mass
Power

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5
Q

What are the 2 catagories forces can be split into

A

Contact forces-when 2 objects are touching
Non contact forces-when 2 objects are seperated

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6
Q

3 examples of contact forces

A

Friction
Air resistance
Tension

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7
Q

3 examples of non contact forces

A

Gravitational forces
Electrostatic forces
Magnetic forces

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8
Q

What happens during friction and air resistance

A

Friction-whenever 2 surfaces are touching and try to move against eachother, tiny bumps in the surface interlock. Creates a friction force
Air resistance-when an object moves through air it collided with air molecules. This created a force which slows the object down

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9
Q

What is meant by an objects centre of mass

A

The single point where an objects weight can be considered to act through

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10
Q

What piece of equipment can be used to measure an objects weight

A

A calibrated spring balance or Newton metre

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11
Q

What are examples of centre of mass used

A

Toppling over-an object falls if it’s centre of mass is outside its base.
Hanging objects-if an object is hung from a string it’ll hang with its centre of mass directly below the point it’s hung from

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12
Q

Why shouldn’t lots of people stand on the top deck of a bus

A

More people on the top deck of buses means the centre of mass will be higher
Therefore a smaller tilt of the bus is required to place the buses centre of mass outside of its wheeled causing the bus to tip

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13
Q

What is the equation for weight

A

Mass x gravitational field strength

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14
Q

What does it mean if a force is said to do work

A

The force causes an object to be displaced through a distance

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15
Q

What is the equation for work done

A

Force x distance

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16
Q

What occurs when work is done agaisnt frictional forces

A

A rise in temperature of the object occurs
Kinetic energy is converted to heat

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17
Q

Why does air resistance slow down a projectile

A

The object does work against the air resistance so kinetic energy is converted into heat slowing down the object

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18
Q

What is inertia

A

An objects mass is also a measure of how different it is to change the objects motion

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19
Q

What is a resultant force

A

The sum of all force acting on an object. If the forces acting on an object are unbalanced it means a resultant force is acting on it

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20
Q

What is the equation for resultant force

A

Mass x acceleration

21
Q

What is Newton’s first law

A

The velocity of an object will only change if the resultant force is acting on it

22
Q

What does Newton’s first law mean for stationary objects

A

If an object is stationary and there’s no resultant force acting on it the object it’ll stay stationary

23
Q

What does Newton’s first law mean for moving objects

A

If an objects moving and no resultant forc actng on it the object will continue moving in the same direction and speed
TMT the object will continue moving at the same velocity

24
Q

What does Newton’s third law state

A

Whenever 2 objects interact the forces they exert on eachotjer are equal and opposite e

25
Q

What are the 2 ways objects can be deformed

A

Elastic vs in elastic deformation

26
Q

What is inelastic deformation

A

An i elastic ally deformed object won’t return to its original shape
For example a car wouldn’t return to its original

27
Q

What is elastic deformation

A

Will return to its original shape. For example a spring

28
Q

What is Hookes law

A

Tells us that the extension of a spring is directly proportional to the force applied to its spring

29
Q

What is the limit of proportionality

A

The point where hookes law breaks down. If a spring is stretched too much it won’t return to its original length when the force stops acting on the spring

30
Q

What happens with a limit of proportionality graph

A

For low forces the graph is a straight line which passes through the origin
When no force acts in the spring there’s no extension

31
Q

What is the required practical for force and extension

A

1)set up your equipenent as in the diagram
2)attach the pointer to the base of the spring ensuring it’s not angled and perpendicular to the ruler. Align the top of the ruler with the top of the spring
3)measure the initial length of the spring without the masses attached
4)add a 10g mass to the base of the spring and record the length of the spring

32
Q

Required practical (2)

A

5)repeat and continue to add masses ensuring that the spring doesn’t oscillate after each weight has been added
6)calculate the extension of the spring for each mass by subtracting the initial length from each different length of the spring
7)convert all masses to weight using w x mg
8)plot the graph of force against extension and calculate the gradient

33
Q

What are the safety precautions to take

A

Don’t stand directly beneath the weights in case they fall offf
Wear safety glasses in case the spring snaps
Place weights gently and avoid oscillating the spring

34
Q

What is the equation for force

A

Spring constant x extension

35
Q

What happens when a force stretches a spring

A

Work is done and energy is transferred into an elastic potential store

36
Q

What happens when you free fall with air resistance

A

Frictional force-air resistance is a frictional force that opposes the motion of an object moving quickly through air
air resistant slows falling object. This force increases as the speed of a falling object increases

37
Q

What is terminal velocity

A

Once the weight force and force due to air resistance are equal the object will stop accelerating
It has reached terminal velocity which is the fastest and object can fall

38
Q

Why is the object slowed when free falling

A

As the object moves through air it must push the air molecules aside to move
This needs force so the object exerts a force on the air. Every action has an equal opposite reaction do the object is slowed

39
Q

What is the equation for momentum

A

Mass x velocity

40
Q

What is the law of conservation of momentum

A

Momentum cannot be created or destroyed so if 2 objects Collide the sum of momentum before collision equals the Sun of momentum after the collision

41
Q

What is stopping distance

A

Thinking distance + braking distance

42
Q

What is the thinking distance

A

The distance travelled between when the driver realised they need brake and when they apply the brakes

43
Q

What is the braking distance

A

The distance the car travels between the driver applying the brakes and the car stopping

44
Q

What factors affect thinking distance

A

Tiredness
Distractions like mobile phones or children
Drugs or alcohol

45
Q

What factors affect braking distance

A

Road conditions - wet or icy
Conditions off the car like car brakes or tyre
Initial car speed-

46
Q

What is the work done while braking

A

When we push the brake pedal, brake pads are pressed onto wheels. This contact causes friction
This causes work to be done
The work done between the brakes and the wheels converts energy from kinetic energy in the wheels to thermal energy
In the brakes
The temperature of the brakes increase

47
Q

What three factors causes more work to be done on tje brakes

A

Higher speed-greater braking force needed
Higjer mass-greater braking force needed
Higjer grip

48
Q

What are the dangers of large decelerations

A

Can cause brakes to overheat and the car to skid. A larger deceleration will cause more stopping force to passengers while harms passengers

Physics Paper 2 (3 decks)

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