Define a radian

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

State the equation to calculate radians

Radian = arc length/radius

Define time period

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

Define frequency

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

Define linear velocity

Rate of change of displacement

measured in m/s

Define angular velocity

Rate of change of angle

measured in rad/s

angular velocity = Ø / t

State the relationship between linear velocity and angular velocity

linear velocity = angular velocity x radius

State the direction of centripetal force

Towards the centre of the circle

Define centripetal force

The overall resultant force acting towards the centre of a circle

State the direction of linear velocity

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

What is the angle between centripetal force and linear velocity

90^{o}

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

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.

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

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- Bigger mass
- Faster velocity
- Smaller radius

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

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

What causes the centripetal force for a planetary orbit

Gravity

What causes the centripetal force for an electron in orbit

electrostatic attraction

What causes the centripetal force for a bung on a string

Tension

What causes the centripetal force for a car cornering

friction

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

Normal reaction resolved horizontally and

friction resolved horizontally

What causes the centripetal force for an airplane banking

lift resolved horizontally

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

Reaction + weight

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

Reaction - weight

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

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.

In the rotor/gravitron ride what forces are acting

Vertical equilibrium where weight is balanced by friction.

Horizontally its accelerating with normal reaction providing the centripetal force.

What cause the centripetal force on a pirate ship?

T - mg cos Ø

What causes the centripetal force on the swing o chairs?

Tension resolved horizontally