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GCSE Physics LTS > Forces 4 - speed/velocity/acceleration/displacement > Flashcards

Forces 4 - speed/velocity/acceleration/displacement Flashcards

1
Q

What does distance tell us, what doesn’t it tell us

A

Distance is how far an object has moved.
Distance does not involve direction (doesn’t say anything about the direction the car moved in only the distance it travelled

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2
Q

Explain why distance is a scalar quantitiy

A

Distance has magnitude but no direction therefore distance is a scalar quantity

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3
Q

Define displacement

A

Displacement includes both the distance an object moves,
measured in a straight line from the start point to the finish point
and the direction of that straight line

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4
Q

Explain why displacement is a vector quantity

A

Displacement includes both magnitude and direction THEREFORE displacement is a vector quantity

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5
Q

Give an example of a displacement measurement

A

380m EAST

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6
Q

Define speed

A

The distance an object has travelled in a given time

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7
Q

Equation that links speed, distance and time

A

Speed = Distance/Time

speed - m/s or km/h
distance - metres or km
time - s or hours

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8
Q

Explain why speed is a scalar quantity

A

Speed has magnitude but no direction therefore speed is a scalar quantity

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9
Q

State the typical speeds of:
walking
running
cycling
car
train
plane
speed of sound in air

A

Typical values may be taken as:
walking ̴ 1.5 m/s
running ̴ 3 m/s
cycling ̴ 6 m/s
car - approx. 13m/s
train - approx. 50m/s
plane - approx. 250m/s
speed of sound in air = 330m/s
the speed of sound can vary - (sound travels faster on warmer days than cooler ones)

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10
Q

State the factors which can affect the speed at which a person can walk, run or cycle

A

The speed at which a person can walk, run or cycle depends on
many factors including:

age, terrain (people move more rapidly on flat ground rather than moving uphill) , fitness and distance travelled

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11
Q

What types of speed varies

A

It is not only moving objects that have varying speed. The speed of
sound and the speed of the wind also vary

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12
Q

Define velocity

A

The velocity of an object is its speed in a given direction

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13
Q

State what we are saying speed or velocity
20m/s
20m/s south

A

20 m/s - stating speed
20m/s south - stating velocity

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14
Q

Explain why velocity is a vector quantity

A

Velocity includes both magnitude and direction, therefore velocity is a vector quanity

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15
Q

Equation for velocity

A

Same for speed
v = s/t

v - velocity
s - distance
t -time

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16
Q

A person walks in a straight line from point A to point B covering a distance of 50m
This takes 40s
Calculate the person’s velocity

A

v = s/t
v=50/40 = 1.25m/s south (the person is south)

17
Q

Explain why the velocity of the car is constantly changing even though a car is travelling at a constant speed in a circle

A

Even though the car is moving with a constant speed, its direction is constantly changing, therefore its velocity is constantly changing

(if an object moves at a constant speed in a circle then its velocity is constantly changing even though its speed is constant)

18
Q

How can the distance be represented if an object moves along a straight line

A

If an object moves along a straight line, the distance travelled can
be represented by a distance–time graph.

19
Q

How can be speed of an object be calculated using a distance-time graph

A

The speed of an object can be calculated from the gradient of its
distance–time graph

20
Q

How can the speed at any particular time be determined for an accelerating object

A

If an object is accelerating, its speed at any particular time
can be determined by drawing a tangent and measuring the
gradient of the distance–time graph at that time.

21
Q

A person walked 100m in a straight line in 100 s
Then stopped for 40 seconds and then walked another 70 m in 50 seconds

A
22
Q

What does an upward sloping curve tell us in a distance-time graph

A

This tells us that the object is constantly increasing in speed (accelerating)

23
Q

How to know the speed at 100s

A

Place a dot on the line - 100 s
draw a tangent to the line
work out gradient of the line

1.75 m/s

24
Q

What does these lines show:
straight line
flat line
steeper straight line
line going downwards
curve - upward/levelling off

A

straight line - object travelling at a constant speed
flat - object is stationary
steepening curve - This tells us that the object is constantly increasing in speed (accelerating)
curve levelling off - object is constantly decreasing in speed (decelerating)
line going backwards - the person is going back to their start point, faster at a constant speed

25
Q

Explain why acceleration is a vector quantity

A

Velocity is a vector quantity as it has both magnitude and direction
The acceleration of an object is the change in its velocity over a given time
therefore acceleration is a vector quantity

26
Q

Define acceleration

A

The acceleration of an object is the change in its velocity over a given time
therefore acceleration is a vector quantity

27
Q

state the equation that links acceleration, change in velocity, time

A

a = ∆ v/t
acceleration = change in velocity/time

a = v - u /t

a = m/s^2
v & u = m/s
time in seconds

28
Q

A car accelerated at 1m/s^2 for 20s
what does this mean

A

The car increased its velocity by 1m/s every second over a 20 second period

29
Q

What does the gradient of a velocity-time graph tell us

A

The gradient of a velocity-time graph represents the acceleration

30
Q

What does a flat line in a velocity-time graph represent
when gradient = 0

A

A flat line/horizontal line shows us that the object is travelling at a constant velocity

31
Q

What does an upward and downward sloping/negative acceleration line represent in a velocity-time graph

A

An upward sloping line shows that the object is accelerating
A downward sloping line shows that the object is decelerating

32
Q

What does a curved line indicate in a velocity-time graph

A

A curved gradient indicates that the object is either accelerating or decelerating at a non-uniform rate

33
Q

How to calculate the distance travelled in a velocity-time graph

A

The total area under the graph tells us the distance travelled in a specific direction (displacement)

distance travelled = area under the graph

or
distance travelled - area under graph (calculated by counting squares)

e.g. 20 squares
each square has an area of 250
20 x 250 = total displacement of 5000 m

34
Q

equation that links velocity, displacement and time

A

v = s/t

velocity = distance travelled in a given direction / time taken

velocity = displacement / time taken

velocity, v in m/s
displacement, s in s
time in s

GCSE Physics LTS (30 decks)

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