Describing motion along a line (5.6.1) (M) Flashcards

1
Q

What is distance?

A

how far an object moves

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2
Q

What type of quantity is distance?

A

scalar - does not involve direction

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3
Q

What is displacement?

A

A measure that 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

What type of quantity is displacement?

A

vector

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5
Q

What type of quantity is speed?

A

scalar - does not involve direction

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6
Q

The speed of a moving object is (…) constant. When people walk, run or travel in a car their speed is (…)

A

rarely

constantly changing

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7
Q

4 needed

What are some factors that can affect the speed at which a person can walk, run or cycle

A
  • age
  • terrain
  • fitness
  • distance travelled
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8
Q

What is the typical speed of walking?

A

∼ 1.5 m/s

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9
Q

What is the typical speed of running?

A

∼ 3.0m/s

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10
Q

What is the typical speed of cycling?

A

∼ 6.0m/s

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11
Q

What are the typical speeds of a car, train and aeroplane?

A

car - 13/30m/s

train - 50m/s

aeroplane - 250m/s

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12
Q

Do the speed of sound and the speed of the wind vary or stay the same?

A

vary

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13
Q

What is the typical value for the speed of sound in air?

A

330m/s

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14
Q

What is the velocity of an object?

A

its speed in a given direction

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15
Q

What type of quantity is velocity?

A

vector

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16
Q

How can something in a circular motion (e.g. satellites), have constant speed but have changing velocity?

A

If something is in circular motion, its direction is constantly changing

17
Q

How can the speed of an object e calculated from a distance-time graph?

A

Calculate the gradient

18
Q

How can speed at any particular time be determined from a distance-time graph?

A

by drawing a tangent at that point and measuring the gradient

19
Q

What is acceleration?

A

the rate of change of velocity

20
Q

How would you describe an object that is slowing down?

A

It is decelerating

21
Q

Falling objects accelerate at (…)m /s2

22
Q

A typical acceleration for a car is (…)m/s2

23
Q

How can the acceleration be calculate from a velocity-time graph?

A

Calculating the gradient

24
Q

How can the distance travelled by an object (or displacement of an object) can be calculated from a velocity-time graph?

A

by calculating the area under the graph

may need to find area using triangles or trapezium area calculations

25
What is uniform acceleration?
When the rate of change of velocity is constant v2 - u2 = 2as
26
Explain what happens when an object falls through a fluid
An object falling through a fluid initially accelerates due to the force of gravity. Eventually the resultant force will be zero and the object will move at its terminal velocity (no resultant force, velocity constant so acceleration is zero)
27
# 4 marker Why does a car have a maximum speed?
there is a maximum forward force (provided by the motor) as the speed of the car increases, air resistance increases until air resistance is equal in size to forward force so the car can no longer accelerate
28
# 4 marker (indicative) Describe what happens to the braking distance if speed doubles (refer to kinetic energy in the answer)
* doubling speed increase the kinetic energy * kinetic energy increases by a factor of 4 * work done (by brakes) to stop the car increases * work done increases by a factor of 4 * work done is force × distance and braking force is constant * so if work done increases by 4 then the braking distance must increase by 4
29
How would changing the shape of a car so that it is more streamlined affect its top speed?
decreases surface area so less air resistance so reaches a higher speed
30
In circular motion, in which direction is the resultant force?
Towards the centre
31
# 2 marks - key exam technique As an object moves along a runway, its acceleration decreases even though the force/power remains constant, why is this?
As speed increases, air resistance increases reducing the resultant force
32
# 4 marks Explain the changing motion of the skydiver in terms of the forces acting on the skydiver
initially air resistance is less than weight / gravity so the skydiver accelerates acceleration causes the air resistance to increase resultant force decreases to zero so the skydiver falls at terminal velocity
33
# 3 marks Explain why a skydiver reaches a much higher speed when jumping from a higher height?
The higher the altitude the less dense the air so air resistance on the skydiver was less so skydiver was able to accelerate for a longer time before reaching terminal velocity