Circular Motion

Question 1

Angular displacement

Answer 1

The angle through which an object moves in a given time

Measured in radians

Question 2

Angular displacement formula

Answer 2

s=rθ

Question 3

Angular displacement for a full circle

Answer 3

2π radians

Question 4

Radians to degrees and vice versa

Answer 4

Shift
Set up
2

Question 5

Linear velocity

Answer 5

Rate of change of linear displacement

Measured in meters/second

Question 6

For an object in circular motion, its linear velocity is what

Answer 6

Tangential to the objects circular path

Constantly changing as the object moves around in a circle

Question 7

Angular velocity equation

Answer 7

w=△θ/△t

Question 8

Angular velocity

Answer 8

Rate of change of angular displacement

Measured in radians/second

Question 9

rpm

Answer 9

Revs per minute
How many revolutions completed in a minute
rms(revs^-1)=Frequency=rpm/60

Question 10

revs^-1 into rads^-1

Answer 10

x2π

Question 11

Angular velocity given frequency

Answer 11

2πf

Question 12

Angular velocity given time period

Answer 12

2π/T

Question 13

Linear velocity given frequency

Answer 13

2πrf

Question 14

Linear velocity given time period

Answer 14

2πr/T

Question 15

Frequency

Answer 15

Number of complete revolutions per second

Question 16

Is a ball swung around someone’s head accelerating if traveling at a constant speed in a circle

Answer 16

Yes
Speed is constant
But velocity is constantly changing since constantly changing direction
Acceleration = Change in velocity/time

Question 17

What must act on a ball to keep it moving in a circular path when swung around a head

Answer 17

A resultant force
Centripetal force
Always acting towards the centre of rotation
Coming from the tension

Question 18

What happens if the string swinging a ball in a circle snaps

Answer 18

No longer accelerates towards the centre
Continues moving at the same speed in the same direction as when the string snapped
Travels in a parabolic path in free fall from the side perspective (acceleration acting vertically down)
From above follows a tangential path, following Newton’s first law

Question 19

Centripetal acceleration

Answer 19

Acts towards the centre of rotation and keeps objects in circular motion along with the centripetal force

Question 20

What are the centripetal force and centripetal acceleration always perpendicular to

Answer 20

(linear) Velocity

Question 21

What happens if the centripetal force increases

Answer 21

Either remains the same distance from the centre but at an increased velocity
Or moves closer to the centre and remains at the same velocity

Question 22

What happens if the centripetal acceleration decreases

Answer 22

Either remains at the same distance from the centre but travels with a smaller velocity
Or moves further from the centre and continues with the same velocity

Question 23

Centripetal acceleration for linear velocities

Answer 23

v^2/r

Question 24

Centripetal acceleration for angular velocities

Answer 24

w^2r

Question 25

Examples of centripetal forces

Answer 25

``` Gravitational attraction Friction Magnetic force Reaction and weight Tension Lift and weight ```

Question 26

What forces contribute to the centripetal force

Answer 26

Any components of forces acting towards the centre of rotation

Question 27

Centripetal force greater than maximum

Answer 27

Circular motion does not happen Force is too weak to maintain circular motion String breaks, car skids off roundabout

Question 28

Centripetal less than or equal to maximum

Answer 28

Circular motion happens

Question 29

What happens if a car enters a bend at a speed higher than the maximum speed

Answer 29

Centripetal force is greater than the maximum friction Car will skid off and move to a greater radius Circular motion couldn't be maintained at that radius

Question 30

Other phrases for reaction

Answer 30

Normal contact | Support force

Question 31

What must be taken into account in vertical circular motion

Answer 31

Force acting readily (tension, reaction) | Weight (vertical component)

Question 32

Increasing speed for non fixed radius

Answer 32

Centripetal force the same | Radius increases

Question 33

Increasing speed for fixed radius

Answer 33

Centripetal force increases

Question 34

Decreasing speed for non fixed radius

Answer 34

Centripetal force the same | Radius decreases

Question 35

Decreasing speed for fixed radius

Answer 35

Centripetal force decreases

Question 36

Centripetal force equation on the underside of the top of a loop in circular motion

Answer 36

Fcentri=W+R

Question 37

Centripetal force equation on top of a loop in circular motion

Answer 37

Fcentri=W-R

Question 38

Centripetal force equation on the bottom of a loop in circular motion

Answer 38

Fcentri=R-W

Question 39

For a ball on a string in vertical circular motion where is tension maximum and why

Answer 39

Bottom Fcentri=T-W For Centripetal force to remain constant, the tension must be greatest here since weight is constant

Question 40

For a ball on a string in vertical circular motion where is tension minimum and why

Answer 40

Top Fcentri=T+W For Centripetal force to remain constant, the tension must be smallest here since weight is constant

Question 41

Does the highest speed a car can travel over the hill change for a car with greater mass

Answer 41

No Stays the same since v max = root (gr) g is constant and so is r so vmax stays the same Mass is not included in the equation/vmax independant of mass mv^2/r=mg m will cancel because although two different masses being compared when working out the vmax its the mass of the same object

Question 42

For a conical pendulum, what is the effect of increasing the velocity

Answer 42

Tension in the vertical direction must stay the same as it must be equal to the weight since in vertical equilibrium Fcentri will increase since the tension in the horizontal direction will increase So radius must increase Meaning that the angle to the vertical will be greater

Question 43

Why will a ball being swung in horizontal motion never be perfectly horizontal

Answer 43

The weight of the wall acts vertically down In order for it to be in vertical equilibrium there must be a vertical component of tension of the centripetal force Meaning that it will always be angled by some amount