3.1 Motion Flashcards

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1
Q

How is average speed calculated?

A

Average speed (ms-1) = Distance Travelled (m)/Time Taken (s)

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2
Q

What is gradient equal to on a distance time graph?

A

The gradient is equal to speed.
If the gradient is 0, the object is stationary.

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3
Q

What is instantaneous speed?

A

Instantaneous speed is the speed of something over a short interval of time.

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4
Q

What is the difference between distance and displacement?

A

Displacement shows how far something is from the starting point, distance shows the overall total of how far something has travelled.

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5
Q

What is the difference between speed and velocity?

A

Speed is scalar and only has magnitude, velocity is vector and has both magnitude and direction.

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6
Q

How is average velocity calculated?

A

Average Velocity (ms-1) = Change in Displacement (m)/Time Taken (s)

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7
Q

How is velocity determined from a displacement time graph?

A

Velocity is calculated from the gradient, or on a curve, by drawing a tangent.

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8
Q

How is acceleration defined?

A

Acceleration is the rate of change in velocity.
Acceleration (ms-2) = Change in Velocity(ms-1)/Time Taken (s)

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9
Q

How is acceleration determined from a velocity time graph?

A

Acceleration is calculated from the gradient of the graph.

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10
Q

How is displacement determined from a velocity time graph?

A

Displacement is calculated from the area of the graph.

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11
Q

What type of motion is SUVAT used for?

A

Motion in a straight line with constant acceleration.

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12
Q

What are the SUVAT equations?

A

v=u+at
s=ut+1/2at²
s=vt-1/2at²
s=1/2(u+v)t
v²=u²+2as

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13
Q

What is meant by free fall?

A

When an object is accelerating under gravity, it is said to be in free fall.

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14
Q

What is the value of acceleration due to gravity?

A

9.81ms-2

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15
Q

What is the electromagnet/trapdoor method of determining g?

A
  • An electromagnet holds a small steel ball above a trapdoor.
  • When the current is switched off, a timer is triggered and the electromagnet will demagnetise and the ball falls.
  • When it hits the trapdoor, electrical contact is broken and the timer stops.
  • The value for g is calculated from the height of the fall - measured with a metre rule - and the time taken.
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16
Q

What is the light gate method of determining g?

A
  • Light gates with two light beams, detectors and a timer connected on a software can be used.
  • When the ball is dropped and falls through the first beam, light is interrupted and the timer starts.
  • When it falls to the second beam, the timer stops.
  • The value for g is calculated from the height between the light gates - measured with a metre rule - and the time taken.
17
Q

What is the picture taking method of determining g?

A
  • A small metal ball is dropped from rest next to a metre rule, and its fall is recorded on video, or pictures are taken with a rapid-fire repeating mode.
  • Instead, a stroboscope illuminates with rapid flashes and the camera shutter is held open which produces many photos of the fall.
  • The position of the ball at regular intervals is recorded against the metre rule. Time taken is measured with a stopwatch in frame of the camera.
18
Q

Describe how data from the determining g experiments can determine g.

A

Plot a graph of s against t². The value of g is determined from s=ut+1/2at² but s=1/2gt² can be used as it’s dropped from rest.

19
Q

How is stopping distance defined?

A

Stopping Distance = Thinking Distance + Braking Distance

20
Q

How is thinking distance defined?

A

Thinking distance is the distance moved between the driver seeing an obstruction and applying the brakes, it depends on the driver’s reactions.

21
Q

What is the equation for thinking distance?

A

Thinking Distance = Reaction Time x Speed of the Car

22
Q

What causes thinking distance to vary?

A

If the driver is tired, under the influence, or speed is increased, thinking distance increases.

23
Q

How is braking distance defined?

A

Braking distance is the distance moved after applying the brakes until the vehicle stops.

24
Q

What causes braking distance to vary?

A

It will increase if the mass is large, velocity is higher, it is raining/icy/muddy, or car brakes/tyres are worn, which both result in less friction.