Circular Motion

Question 1

Define a radian

Answer 1

A radian is the angle subtended by a circular arc with a length equal to the radius of the circle.

Question 2

State the equation to calculate radians

Answer 2

Radian = arc length/radius

Question 3

Define time period

Answer 3

Time period (T) is the time taken for one complete revolution. It is measured in seconds (s)

Question 4

Define frequency

Answer 4

Frequency is the number of revolutions per second. It is measured in Hertz (Hz)

Question 5

Define linear velocity

Answer 5

Rate of change of displacement

measured in m/s

Question 6

Define angular velocity

Answer 6

Rate of change of angle

measured in rad/s

angular velocity = Ø / t

Question 7

State the relationship between linear velocity and angular velocity

Answer 7

linear velocity = angular velocity x radius

Question 8

State the direction of centripetal force

Answer 8

Towards the centre of the circle

Question 9

Define centripetal force

Answer 9

The overall resultant force acting towards the centre of a circle

Question 10

State the direction of linear velocity

Answer 10

at a tangent to the circle and always at a right angle to the centripetal force

Question 11

What is the angle between centripetal force and linear velocity

Answer 11

90^o

Question 12

How can an object move at constant speed but still be accelerating?

Answer 12

if it is moving in a circular path it is constantly changing direction. That must means its velocity is constantly changing. A change in velocity means it is accelerating. It is always accelerating towards the centre of the circle.

Question 13

State 3 factors that can increase the size of the centripetal force

Answer 13

1. Bigger mass
2. Faster velocity
3. Smaller radius

Question 14

Describe a practical to prove the relationship between linear velocity and centripetal force

Answer 14

1. Use a bung attached to some string.
2. Add masses to the end of the string to vary the centripetal force
3. Swing the bung in a circular path and time for 10 revolutions.
4. Calculate the velocity
5. Keep the mass of the bung and radius of the circle constant, whilst varying the centripetal force by changing the number of masses.
6. Plot a graph of centripetal force against velocity.
7. To prove the relationship the graph should be a straight line that passes through the origin.

Question 15

What causes the centripetal force for a planetary orbit

Answer 15

Gravity

Question 16

What causes the centripetal force for an electron in orbit

Answer 16

electrostatic attraction

Question 17

What causes the centripetal force for a bung on a string

Answer 17

Tension

Question 18

What causes the centripetal force for a car cornering

Answer 18

friction

Question 19

What causes the centripetal force for a car cornering on a banked slope.

Answer 19

Normal reaction resolved horizontally and

friction resolved horizontally

Question 20

What causes the centripetal force for an airplane banking

Answer 20

lift resolved horizontally

Question 21

What causes the centripetal force for a rollercoaster at the top of a loop the loop

Answer 21

Reaction + weight

Question 22

What causes the centripetal force for a rollercoaster at the bottom of a loop the loop

Answer 22

Reaction - weight

Question 23

Why is the normal reaction for a rollercoaster greater at the bottom of a loop the loop that at the top

Answer 23

At the top the weigh helps contribute to the centripetal force.

At the bottom the reaction force has to overcome all the weight and then provide the centripetal force.

Question 24

In the rotor/gravitron ride what forces are acting

Answer 24

Vertical equilibrium where weight is balanced by friction.

Horizontally its accelerating with normal reaction providing the centripetal force.

Question 25

What cause the centripetal force on a pirate ship?

Answer 25

T - mg cos Ø

Question 26

What causes the centripetal force on the swing o chairs?

Answer 26

Tension resolved horizontally