5.2 Circular motion

What are radians?

used instead of degrees

How many radians in one circle?

2π

What is period?

time taken for an object to travel a full circle

What is frequency?

number of full circles completed in one second

F=

1/T

What is angular velocity?

the rate of change of angle

What is centripetal force?

the net force which acts perpendicular to the direction of velocity, towards the centre of the circle

What is the equation for speed of an object?

v=ωr

What are the equations centripetal acceleration?

a=v²/r=ω²r

How do you find centripetal force using centripetal acceleration?

sub in F=ma

Where can centripetal force come from?

gravitational fields, tension in rope, friction

Describe an experiment to investigate circular motion

1. tie a bung (mass m) to a string and thread it through a glass tube

2. at the other end of the string suspend a weight (mass M) from it which provides centripetal force F=Mg

3. whirl string in a circle, time taken for one complete rotation is recorded with a stopwatch and the radius is measured with a ruler

4. alter the mass of the weight and repeat the experiment

centripetal force=weight at end of string so Mg=mv²/r

using radius and time for one oscillation, velocity can be determined

plot a graph v² against M, a straight line graph which passes through the origin should be produced