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A-level AQA Physics > 13 Circular Motion > Flashcards

13 Circular Motion Flashcards

(64 cards)

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1
Q

What is the Time Period (T) for circular motion?

A

The time for one revolution.

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2
Q

What is the frequency (f) in circular motion?

A

number of revolutions per seconds.

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3
Q

What is frequency measured in in circular motion?

A

hertz (Hz)

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4
Q

What is linear speed (v) in circular motion?

A

The distance travelled per second.

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5
Q

What is the symbol for linear speed?

A

v

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6
Q

What is the definition of a radian.

A

An angle of 1 radian results in an arc with a length equal to the radius of the circle.

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7
Q

What is the formula to find an angle in radians?

A

arc length / radius of the circle

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8
Q

What is 180° in radians?

A

π rad.

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9
Q

What equation connects frequency and time period?

A

f= 1/ T

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10
Q

What is angular displacement (θ) in circular motion?

A

the angle described by the object moving in a circle, and is measured in degrees or radians.

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11
Q

What is angular speed (ω) (angular velocity)?

A

The angular displacement per second and is measured in rad s^-1.

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12
Q

What is the symbol for angular speed?

A

ω

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13
Q

What is the equation for average linear speed?

A
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14
Q

What are the 2 equations for angular speed(ω)?

A
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15
Q

What is the equation for linear speed (v)?

A
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16
Q

State Newton’s 1st law.

A

A body will continue with a constant velocity (i.e. in a straight line) unless acted upon by an unbalanced (resultant) force.

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17
Q

If the metal ball is clearly not moving in a straight line, what must be acting on it?

A

An unbalanced (resultant) force acting on it.

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18
Q

What is an unbalanced force?

A

a resultant force.

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19
Q

With a whirligig, what must happen in the string if the rubber bung is to move with a greater linear speed whilst the mass and radius remain constant?

A

It increases.

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20
Q

With a whirligig, what must happen to the tension in the string if the rubber bung is to move in a circle of bigger radius whilst the mass and linear speed remain constant?

A

It decreases.

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21
Q

In a whirligig, what must happen to the tension in the string if a more massive rubber bung is used whilst the linear speed and radius are kept constant?

A

It increases.

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22
Q

In circular motion, when the speed is doubled, the force…

A

x4

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23
Q

In circular motion, when the radius is doubled, the force…

A

halves.

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24
Q

In circular motion, when the mass is doubled, the force…

A

doubles

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25
In circular motion, when the force is doubled, the acceleration...
doubles.
26
What is the equation linking: Force (F), mass (m), radius (r) and speed (v)
27
For an object to act in a curved path, what must there be?
A force acting on the object towards the centre of the curved path to prevent the object going off at a tangent.
28
What is the definition of centripetal force?
Any resultant force which stops an object from moving off at a tangent from a circular path is called a centripetal force. It always acts towards the centre of the curved path.
29
When an object is spun in a circle, the magnitude of the centripetal force has to be bigger if: -The objects mass gets ............ -The speed of the object gets ............ -The radius of the curvature of the path gets ............ if ω is constant.
When an object is spun in a circle, the magnitude of the centripetal force has to be bigger if: -The objects mass gets **bigger** -The speed of the object gets **bigger** -The radius of the curvature of the path gets **bigger** if ω is constant.
30
What cause the centripetal force of the ball on the end of the chain in the hammer throw?
The tension in the chain.
31
What cause the centripetal force of the earth in orbit around the sun?
gravitational attraction.
32
What cause the centripetal force of a car moving around a bend in the road?
friction between the tyre and the road.
33
What cause the centripetal force of an electron orbiting the nucleus of an atom?
electromagnetic force
34
What is the definition of centripetal acceleration?
Acceleration which is directed towards the centre of a curve causing an object to follow a circular path.
35
Why is the equation for centripetal force F= mv^2/r
because F= ma
36
As the frequency of rotation of the disc increases, which car will fly off first?
The one near the edge because it has a bigger radius.
37
When a track bends, what is needed to prevent the car from moving off at a a tangent?
A force towards the centre of the curve.
38
For a car taking a bend on the flat, what is the force that prevents the car from going of at a tangent provided by?
sideways friction.
39
What can limit sideways friction?
The road surface and the condition's of the cars tyres.
40
What is sideways friction the same as in equations?
centripetal force.
41
If the sideways friction is not large enough, what will happen to the car?
It will skid an go off at a tangent.
42
Which forces are the ones that contribute to the required centripetal force
The forces that point towards the centre of the track
43
On a flat track, what provides all of the centripetal force?
The sideways friction between the tyres and the track. *All the other forces act straight up or down.*
44
On a banked track, what does the normal contact force the track exerts on the car have?
A vertical component and a horizontal component towards the centre of the track.
45
Why does a banked track help a car to turn?
Because some of the normal contact can provide some of the required centripetal force.
46
What is larger when a banked track is steeper?
The larger the portion of the normal contact force from the track that points towards the centre of the bend.
47
Is all the frictional force between the track and the tyres pointing towards the centre of the banked track?
No, but the amount of force lost, is more than made up by the force gained from the track banking.
48
In what direction is the resultant force acting on the plane?
In a direction towards the centre of the curve.
49
What does the horizontal component of the lift force which provides the resultant centripetal force cause the plane to do?
turn.
50
What must a satellite be lifted to?
The correct height above earth.
51
What ensures that a satellite has the correct speed in the required direction?
Small on-board rockets are fired.
52
What is the centripetal force keeping a satellite in a circular path and preventing it from going off at a tangent?
Its weight.
53
What is the centripetal acceleration of a satellite?
The acceleration due to gravity at the height of the satellite.
54
Why is the centripetal acceleration of a satellite the acceleration due to gravity at the height of the satellite?
Because the centripetal force requires for the satellite's circular motion is caused by the satellite's weight.
55
What is the gravitational field strength at the height of the international space station?
8.7 N kg^-1
56
Why do astronauts on the international space station feel weightless?
The ISS and the astronauts inside all have the same acceleration towards earth. Consequently, there is no normal contact force on the astronauts, so they feel weightless.
57
When do you feel weightless?
When the only force acting on you is your weight.
58
What is the GPS?
A constellation of 27 satellites in orbit around the earth. 24 in operation and 3 extra in case one fails.
59
What was the GPS developed by?
The US military.
60
What is the GPS receiver's job?
To locate 4 or more of these satellites and use maths to calculate its own position.
61
What is the mass of a satellite?
1600kg
62
At what height does a satellite orbit above the earth's surface?
19,300kg
63
How many rotations does a satellite do of the earth each day?
2 complete rotations.
64
Explain why a body moving at a constant speed in a circular path needs a resultant force acting on it.
-The objects direction is continuously changing. -So the object's velocity must be changing because velocity is a vector and has direction. -If the velocity is changing then the object must have acceleration. -Acceleration is a vector so it must have direction. -So, resultant force towards the centre.

A-level AQA Physics (13 decks)

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