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Phy > Scalars and Vectors > Flashcards

Scalars and Vectors Flashcards

1
Q

What is a vector?

A

A quantity of unit and magnitude with direction

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2
Q

What is a scalar?

A

A quantity of unit and magnitude without direction

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3
Q

What is magnitude?

A

The size of something

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4
Q

What is the difference between distance and displacement?

A

Distance is how far an object has travelled but displacement is how far away an object is from where it started

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5
Q

When do you use a parallelogram of forces?

A

To find the resultant force acting on an object, when the two forces are working in different directions

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6
Q

How do you draw a parallelogram of forces?

A

Draw your line to scale
Find the angle in the question and draw the line to scale
Repeat on the other side but flipped
Draw from one side to the other and measure
Times the measurement by the scale to get the resultant force

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7
Q

What is a moment?

A

The turning effect of a pivot point

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8
Q

What is the pivot/ fulcrum?

A

The hinge or point of rotation

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9
Q

What is the equation for moment?

A

moment = perpendicular distance from force to point x force

M = d x f
Nm = M x N

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10
Q

What is equilibrium?

A

When the sum of the clockwise moment equals the sum of the anticlockwise moments. The moments are balanced and there is no overall turning effect

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11
Q

What is the centre of mass?

A

The point of an object at which is mass can be thought of is being concentrated

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12
Q

How to find the centre of mass of symmetrical objects

A

Mark the axis
Follow the lines to the centre of the object and mark the point

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13
Q

What is the suspension method?

A

Drill a small hole in the object and hang it up so that it is free to swing
hang a plum line- a piece of string with weight hanging on it from the same point this lets you mark the vertical line directly below this suspension point
drill another hole at a different location within the object
again hang the plum line to determine the vertical and market on the point of which the two marked line cross is the centre of mass

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14
Q

What is stopping distance?

A

how long it will take for an object to stop moving

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15
Q

What two parts make up the stopping distance of a car?

A

thinking distance and breaking distance

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16
Q

what is the thinking distance?

A

The distance travelled during the reaction time of the driver

17
Q

what is the breaking distance?

A

The distance travelled while the brakes are applied

18
Q

what is the formula for the stopping distance?

A

stopping distance = thinking distance + breaking distance

19
Q

What’s the formula for the thinking distance?

A

thinking distance = initial velocity
x reaction time

20
Q

What is terminal velocity?

A

This is reached when the air resistance from falling reaches the same force as the weight of the object falling so the speed reached a constant point

21
Q

what is drag?

A

The force pushing on an object in the opposite direction of movement whilst it is in a liquid of gas

22
Q

why is drag caused?

A

The object has to push away the particles

23
Q

what things affect drag?

A

speed of object
Shape of object- wide and flat means more drag
Viscosity of liquid

24
Q

What is momentum

A

The tendency of the object to keep moving in the same direction. It is difficult to change the direction of movement of an object with a lot of momentum

25
Q

How does momentum work

A

The bigger the momentum of an object, the harder it is to stop that object moving. The momentum of an object depends on its mass and velocity

26
Q

What is the formula for momentum

A

momentum = mass * velocity
P = m * v

27
Q

What are the units of measurements for momentum

A

kgm/s
kilogram metres per second

28
Q

Is momentum a scalar or vector?

A

Vector because it is a product of mass and velocity, velocity is a vector, so momentum is also a vector

29
Q

How do you calculate the velocity of objects after a collision?

A
  1. Calculate the total momentum before collision: P = m x v for both objects and add them together
  2. Calculate the total mass: add them together
  3. Rearrange the equation for velocity: v = P/m
30
Q

What is the equation for impact force?

A

force = change in momentum / time taken

31
Q

How to reduce impact force?

A

Increase the time taken
Decrease the mass
Decrease the change in velocity - apply the brakes

32
Q

Why do we work out the average impact force

A

Because the rate of deceleration will vary during collision

33
Q

What is the formula for deceleration?

A

change in velocity / impact time

34
Q

What is impact time?

A

How long it takes for a moving object to completely stop after a collision takes place

35
Q

How do seatbelts save lives?

A

Seat belts increase the contact time by stretching the seat belt. This means the change in momentum stays constant, therefore the impact force is reduced.

Phy (3 decks)

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