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Pro Physics > P10,P11 > Flashcards

P10,P11 Flashcards

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1
Q

Explain what happens to a falling object in terms of speed and friction

A
  • To start with, the force of gravity is more than the frictional force so it accelerates
  • As the speed increases, the friction also increases gradually, reducing the acceleration until the frictional force is equal to the accelerating force so the resultant force is zero
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2
Q

What does terminal velocity depend on in terms of the type of object?

A

Shape and area

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3
Q

What is the accelerating force acting on all objects and what would happen without it?

A
  • Gravity
  • On the Moon, where there is no air resistance, bricks and feathers dropped simultaneously will hit the ground together. This is because there is no frictional force acting on the objects.
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4
Q

What is required to make something start moving, speed up or slow down?

A

A resultant force

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5
Q

What will a non-zero resultant force produce?

A

Acceleration or deceleration in the direction of the force

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6
Q

What is the unit used for momentum?

A

kg m/s
kilogram metres per second

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6
Q

In a closed system, what can be said about the momentum before and after a collision?

A

The total momentum before is equal to the total momentum afterwards.

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7
Q

What quantity is equal to the force experienced in a collision?

A

The rate of change of momentum

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8
Q

Explain how a seatbelt improves a passenger’s safety during a collision

A
  • Passengers must decelerate from the vehicle’s velocity at impact to zero, meaning they undergo a fixed change of momentum
  • The force they experience is equal to the rate of change of momentum
  • Seatbelts increase the time over which the force is applied, reducing the rate of change of momentum and thereforce reducing the force applied, resulting in fewer injuries
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9
Q

If a car travelling at a velocity of +10m/s suddenly turns around and continues at the same speed, what is its new velocity?

A

-10m/s

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10
Q

What is the name for the pulling force that a string or cable exerts when something or someone pulls on it?

A

Tension

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11
Q

What does a curved line show on a speed-time graph?

A
  • a curved line shows that an object is accelerating or decelerating at a rate that is not constant
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12
Q

Unit for acceleration

A

m/s2

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13
Q

When will an object topple?

A

When its centre of mass is located outside its base

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14
Q

What is the resultant force on a stationary object?

A

0

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15
Q

At least how many forces must be acting on an object to stretch, bend or compress it?

A

2

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16
Q

What property of a spring does the spring constant represent?

A

Stiffness

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17
Q

In context of springs, what is extension?

A

The change in length of a spring when a force is applied

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18
Q

What does the area under the force-extension graph represent?

A

Elastic potential energy

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19
Q

Which symbol is used to denote the acceleration due to gravity?

A

g

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20
Q

On the speed-time graph for an object in free fall, what is equal to g?

A

The gradient/slope of the line

21
Q

What is the acceleration of an object at terminal velocity?

A

Zero, the object is moving at a constant speed

22
Q

What is the name of the distance travelled between when the driver realises they need to brake and when they apply the brakes?

A

Thinking distance

23
Q

3 factors that affect the thinking distance of a driver?

A
  • Alcohol
  • Tiredness
  • Distractions
24
Q

What does the gradient on a velocity-time graph show?

A

Acceleration

25
Q

What is gravitational field strength?

A

It is a way of measuring how much gravity there is

26
Q

What can extension be replaced with in the equation for spring force?

A

Compression

27
Q

What must be done to calculate speed at a given time from a distance-time graph for an accelerating object?

A
  • Drawing a tangent to the curve at the required time
  • Calculating the gradient of the tangent
28
Q

What can be said about the resultant force on an object when it is falling at terminal velocity?

A

The resultant force is zero

29
Q

If an object changes direction but remains at a constant speed, is there a resultant force?

A

Since there is a change in direction, there is a change in velocity and so there must be a resultant force

30
Q

Typical value for human reaction time

A

0.2 to 0.9 seconds

31
Q

Give 2 factors which may affect braking distance

A
  • Icy/wet conditions
  • Poor tyres/brakes
32
Q

What is the relationship between acceleration and mass?

A

Inversely proportional

33
Q

How to work out the velocity after a collision of multiple objects?

A
  1. work the total momentum before the event
  2. p = mv
  3. work the total momentum after the event
  4. work total mass after collision
  5. work out new velocity
34
Q

What force keeps an object afloat?

A

Upthrust

35
Q

What are changes in momentum called?

A

Impulses

36
Q

3 Safety Features used in cars

A
  • air bags
  • seat belts
  • crumple zone
37
Q

Which event applies the greatest force to car passengers?

A

Car crash

38
Q

What is the atmosphere?

A

The atmosphere is a thin layer (relative to the size of the Earth) of air round the Earth

39
Q

If the resultant force acting on an object is zero and the object is moving, what happens?

A

The object continues to move at the same speed and in the same direction. So the object continues to move at the same velocity.

40
Q

What is inertia?

A

The tendency of objects to continue in their state of rest or of uniform motion

41
Q

Explain why you don’t move when you lean on a wall, even though you are exerting a force

A
  • You exert a force on the wall and so does the wall back on you (Newton’s 3rd Law)
  • These forces are equal and opposite
  • The resultant force is 0, so you remain stationary
42
Q

What does Newton’s Third Law state?

A

For every force that acts on an object, there will be an equal and opposite force acting on another object.

43
Q

What does Newton’s 2nd Law state?

A

The more mass an object has, the harder it is to accelerate.

44
Q

What does Newton’s 1st Law state?

A

An object remains in the same state of motion unless a resultant force acts on it.

If the resultant force on an object is zero, this means:

45
Q

Dangers of large decelerations

A
  • brakes overheating
  • loss of control
46
Q

Formula for stopping distance

A

Stopping distance = Braking distance + Thinking distance

47
Q

What is weight the same as?

A

Force

48
Q

What happens to the total momentum if the cars are travelling in opposite directions?

A

Total momentum = Momentum A - Momentum B

49
Q

Is force scalar or vector?

A

Vector

50
Q

What is thinking distance?

A

Distance a vehicle travels during driver’s reaction time

51
Q
A

Pro Physics (14 decks)

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