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Physics > Topic 5 - Forces > Flashcards

Topic 5 - Forces Flashcards

1
Q

What is a vector quantity?

A

it has magnitude and direction

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2
Q

Give examples of vector quantities (5)

A
  • force
  • velocity
  • displacement
  • acceleration
  • momentum
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3
Q

What is a scalar quantity?

A

only has magnitude and no direction

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4
Q

Give examples of scalar quantities (7)

A
  • mass
  • speed
  • distance
  • time
  • energy
  • power
  • density
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5
Q

What is the equation to calculate weight?

A

mass x gravity

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6
Q

What will happen to an object with NO resultant force acting on it?

A

either:
- remain stationary
- remain at a constant velocity

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7
Q

What will happen to an object with a resultant force acting on it?

A

accelerate - it could be:
- speeding up
- slowing down
- changing direction

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8
Q

Define a resultant force

A

one force representing multiple forces

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9
Q

Define elastic deformation

A

the object can go back to its original shape after the force has been removed

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10
Q

Define inelastic deformation

A

the object cannot go back to its original shape - it has been permanently deformed

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11
Q

When does inelastic deformation occur?

A

when the limit of proportionality is exceeded

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12
Q

What is Hooke’s Law?

A

The extension of an object is directly proportional to the force applied to it, provided the limit of proportionality hasn’t been exceeded

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13
Q

What is the law of conservation of energy?

A

energy cannot be created or destroyed, only transferred

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14
Q

A moment depends on 2 things:

A
  • the perpendicular force
  • the perpendicular distance
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15
Q

What is the principle of moments?

A

for a system in equilibrium, the sum of the clockwise moments is equal to the sum of the anticlockwise moments

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16
Q

What is a moment?

A

the turning effect of a force

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17
Q

Define speed

A

the rate of change of position

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18
Q

Define velocity

A

the rate of change of position in a give direction

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19
Q

What is the average walking speed?

A

1.5 m/s

20
Q

What is the average running speed?

A

3 m/s

21
Q

What is the average cycling speed?

A

6 m/s

22
Q

Define acceleration

A

the change in velocity in a certain amount of time

23
Q

On a velocity-time graph, what does the gradient of the line represent?

A

acceleration

24
Q

On a distance-time graph, what does the gradient of the line represent?

A

speed

25
Q

How do you find distance on a velocity-time graph?

A

the area under the graph

26
Q

What is drag?

A

the resistance you get in a fluid

27
Q

How do you reduce drag?

A

keeping the shape of the object streamlined

28
Q

Why will an object slow down and stop if it has no force propelling it?

A

friction

29
Q

Describe an object falling

A
  • when it first sets off, the force of gravity is much more than the frictional force slowing it down, so it accelerates
  • as the speed increases, the friction builds up
  • this gradually reduces the acceleration until the frictional force is equal to the accelerating force (so the resultant force is zero)
  • it will have reached its terminal velocity and will fall at a steady speed
30
Q

Define terminal velocity

A

the maximum speed of an object, reached when the forces moving the object are balanced by its frictional forces

31
Q

Name Newton’s 1st law

A

if an object has no resultant force, it will continue to move at a constant velocity or remain stationary

32
Q

Name Newton’s 2nd law

A

resultant force = mass x acceleration
- acceleration is directly proportional to the resultant force
- acceleration is inversely proportional to the mass

33
Q

Name Newton’s 3rd law

A

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

34
Q

Define stopping distance

A
  • the distance travelled between seeing the obstacle and the car reaching 0 m/s
  • thinking distance + braking distance
35
Q

Define thinking distance

A

the distance travelled between seeing the obstacle and applying the brakes

36
Q

Define braking distance

A

the distance travelled between applying the brakes and the car reaching 0 m/s

37
Q

Factors affecting thinking distance:

A
  • tiredness
  • drugs/alcohol
  • distractions
38
Q

Factors affecting braking distance:

A
  • speed
  • road conditions
  • vehicle conditions
39
Q

Describe how you investigate how mass affects acceleration

A
  • set up the ramp on the lowest setting
  • attach a piece of card on to the top of the trolley
  • find the mass of the trolley
  • fasten the pulley to the end of the bench and set up the string
  • set up 2 light gates - one near the top and one near the bottom of the ramp
  • put a mass at the end of the string
  • release the trolley from the top of the ramp and record the speed as it passes through each light gate (using a data logger)
  • repeat adding 100g mass each time
40
Q

What is the relationship between mass and acceleration?

A

when mass increases, acceleration decreases (inversely proportional)

41
Q

Describe how you would investigate how force affects acceleration

A
  • set up the ramp, attach a piece of card to the top of the trolley, find the mass of the trolley
  • fasten the pulley to the end of the bench and set up the string, set up 2 light gates at the top and bottom of the ramp
  • add 5 masses to the mass holder on the end of the string
  • release the trolley and record the time passing through each light gate
  • remove one mass from the stack and add it to the top of the trolley (will keep the total mass constant)
  • repeat for each further mass on the stack
42
Q

What is the relationship between force and acceleration?

A

as force increases, acceleration increases

43
Q

Define inertial mass

A

the ratio of force to acceleration

44
Q

Define momentum

A

Momentum is a quantity of a moving body that is proportional to its mass and velocity - how difficult the object is to stop

45
Q

What is conservation of momentum?

A

In a closed system, the total momentum before an event is the same as after the event.

46
Q

Why are cars designed to slow people down over a longer period of time?

A
  • a longer time means a smaller resultant force because there’s a reduced rate of change of momentum
  • this means the force is smaller so less chance of injury
47
Q
A

Physics (8 decks)

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