6.1 Circular Motion Flashcards
What is the period?
The time to make one full revolution, since the speed v is constant and the object covers a distance of 2pir in a time of T seconds it follows that v = 2pir/T
What is the frequency?
The number of revolutions per second, reciprocal of the period.
What is the angular speed?
w is defined as w = (angle swept out)/(time taken). For a complete revolution the change in the angle swept out is 2pi and time equals t so we have w - 2pi/T. Angular speed has units of radians per second s^-1
How are angular and linear speed related?
w = 2pi/T and v=2pir/T so v = wr
How are angular speed and frequency related?
w = 2pi/T = 2pif
What is centripetal acceleration?
The acceleration of circular motion in which only the velocity direction is changing.
Why will there be acceleration if the speed along the circle is constant?
Because the direction of the velocity keeps changing.
What is the direction of the acceleration?
The direction of the change in velocity.
What is the magnitude and direction of the acceleration?
v^2/r towards the centre of the circle.
How can you combine two formulas to come up with the acceleration?
a = v^2/r = ((2pir/T)^2)/r
= 4pir^2r/T^2 = 4Pi^2rf^2
What is another formula for centripetal acceleration?
a=v^2/r
= (wr)^2/r = w^2r
What does Newtons second law F=ma show tell us about acceleration?
If there is acceleration the there is a force in the same direction as the acceleration.
What is the centripetal force?
In circular motion the centripetal acceleration is towards the centre of the circular path so we must have net force towards the centre which is referred to as the centripetal acceleration.
What happens when a car goes round a bend?
The centripetal force is provided by the friction between the road and the tyres.
What happens when the Earth revolves around the sun?
The centripetal force on the Earth is its gravitational attraction to the sun.
