Angular velocity measured in

Radians per second Symbol is lower case omega, not w

Velocities of all points on string when rotation

w same for all, but linear velocity different.

Why is there centrapetal acceleration

Velocity changing so must be an a towards centre of circle always at 90 degrees to v.

F = ma only true with constant mass and SI units

Why is there a centrapetal force

N2L applies so there must be a centrapetal force as there is a centrapetal acceleration

Normal driving effect of friction

Friction on road from wheel backwards, so friction forwards on wheel from road - doesnt oppose car motion. There is a max to the frictional force, so as v increases eventually r must increase

Friction on road from wheel forwards so from road backwards on wheel - opposes car motion

Friction gains a perpendicular component as friction in new wheel direction, which is the centrapetal force.

Loop de loop physics at the top

N and mg both acting downwards. Falls when it loses contact, which is when N = 0, making mg + N the lowest force it can be (so with such a low v r must decrease to give minimum force of mg) As v up, N increases for enough centripetal

Loop de loop calculating height fallen for energy

h = 0 at the top of the loop where we do our calculations

Work done in circular motion

Zero as no displacement in direction of force (orbits last forever)

Not a real force. Provided by a real force. Is the resultant of all real forces acting on body.

How to solve circular motion Qs

Free body diagram. Resolve forces towards centre of circle with resultant = CF If needed resolve forces at 90 degrees to CF where resultant = 0 NOT statics problems

Why a wider radius turn faster

Higher r when turning so higher v possible before max frictional force (as m is fixed)

Normal circle but with lift force at angle. Lift always at 90 degrees to wings. Also need to speed up when turning so vertical component still balances weight once some component horizontal.

Why angle theta increases when angular velocity of conical pendulum increases

So vertical equilibrium maintained as Tcostheta = mg so costheta must decrease so theta increases

What happens if too fast over road bump

Max centripetal force is when N=0 so mg. If too fast, will 'jump' the car as radius increases

Why normal reaction force is significantly reduced

Ultimately is just trying to limit centrapetal force, but can also see as weight being 'used up' as centripetal so less going into surface.

Radius of a diagonal swing spinning

The radius of the actual 2D circle it takes, not the swing rope

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Physics Circle Motn

Physics Autumn Y13

Question	Answer
Angular velocity measured in	Radians per second Symbol is lower case omega, not w
Frequency of rotations measured in	Hz
Velocities of all points on string when rotation	w same for all, but linear velocity different.
Why is there centrapetal acceleration	Velocity changing so must be an a towards centre of circle always at 90 degrees to v.
N2L requirements	F = ma only true with constant mass and SI units
Why is there a centrapetal force	N2L applies so there must be a centrapetal force as there is a centrapetal acceleration
Normal driving effect of friction	Friction on road from wheel backwards, so friction forwards on wheel from road - doesnt oppose car motion. There is a max to the frictional force, so as v increases eventually r must increase
Skidding wheels	Friction on road from wheel forwards so from road backwards on wheel - opposes car motion
Car wheels turning	Friction gains a perpendicular component as friction in new wheel direction, which is the centrapetal force.
Loop de loop physics at the top	N and mg both acting downwards. Falls when it loses contact, which is when N = 0, making mg + N the lowest force it can be (so with such a low v r must decrease to give minimum force of mg) As v up, N increases for enough centripetal
Loop de loop calculating height fallen for energy	h = 0 at the top of the loop where we do our calculations
Work done in circular motion	Zero as no displacement in direction of force (orbits last forever)
'Apparent weight'	NCF
Centripetal force	Not a real force. Provided by a real force. Is the resultant of all real forces acting on body.
How to solve circular motion Qs	Free body diagram. Resolve forces towards centre of circle with resultant = CF If needed resolve forces at 90 degrees to CF where resultant = 0 NOT statics problems
Why a wider radius turn faster	Higher r when turning so higher v possible before max frictional force (as m is fixed)
Banking aircraft	Normal circle but with lift force at angle. Lift always at 90 degrees to wings. Also need to speed up when turning so vertical component still balances weight once some component horizontal.
Why angle theta increases when angular velocity of conical pendulum increases	So vertical equilibrium maintained as Tcostheta = mg so costheta must decrease so theta increases
What happens if too fast over road bump	Max centripetal force is when N=0 so mg. If too fast, will 'jump' the car as radius increases
Why normal reaction force is significantly reduced	Ultimately is just trying to limit centrapetal force, but can also see as weight being 'used up' as centripetal so less going into surface.
Radius of a diagonal swing spinning	The radius of the actual 2D circle it takes, not the swing rope
Actually evaluate answer don't just write the variables
Read through the practical skills booklet before exam

Created by: Pyrogearos2

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