Circular Motion Flashcards
To revise the circular motion topic
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
State the relationship between linear velocity and angular velocity
linear velocity = angolar 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 centripetal force
Towards the centre of the circle
State the direction of linear velocity
at a tangent to the circle
What is the angle between centripetal force and linear velocity
90
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
Bigger mass
faster velocity
Smaller radius
Describe a practical to prove the relationship between linear velocity and centripetal force
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. Plot a graph of centripetal force against velocity squared. 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
upthrust 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.
