Slide 1

Slide 2

What is a lever arm?

Slide 3

Distance from the axis of rotation to where a force is applied

Slide 4

Slide 5

When the net torque on an object is equal to ZERO Balanced objects (not rotating) are in rotational equilibrium

Slide 6

Why will a non rotating bike wheel topple while a spinning wheel will stay upright?

Slide 7

Conservation of Angular Momentum, the direction of the angular momentum cannot change without an outside torque being applied.

Slide 8

How might you kick a football so that it leaves the foot with no rotation?

Slide 9

Kick it (apply a force) directly to the COG If kicked above or below COG, then torque would be applied and rotation would occur

Slide 10

How would you move the circle so that the rod was more balanced?

Slide 11

Move circle closer to the axis, thereby giving it a lower lever arm and therefore a lower torque is being produced by it

Slide 12

Why when Mr. Schober flipped over the spinning wheel while sitting on the stool did he then start to rotate?

Slide 13

Cons. Of angular momentum, Schober, wheel and stool are all a closed system By flipping the direction of the wheel we changed its L, so then Schober and stool rotated in opposite direction, so that the total L of the whole system stayed constant

Slide 14

which direction did Schober start rotating the original direction that the tire was rotating??, or the new direction that the tire was rotating? ?

Slide 15

Original Direction

Slide 16

True or False? In order to balance, the total forces on both sides of the axis of rotation need to be equal.

Slide 17

FALSE The total torque on each of the axis needs to be equal AKA. Total torque on left side = total torque on right side Torque.. NOT Force

Slide 18

How can a person reduce the rotational inertia of their body?

Slide 19

Making their radius smaller by pulling their body into a tight ball that is close to whatever axis they may be rotating on

Slide 20

Ice skater is spinning with arms and legs out, then pulls them in tight to their center? What happens? And Why?

Slide 21

They gain a higher rotational speed, because of the law of conservation of angular momentum.

Slide 22

Solid cylinder and hoop each of the same mass and radius roll down an incline. Which will make it down the incline faster? Why?

Slide 23

Solid Cylinder because it has a lower rotational inertia. Because more of its mass is concentrated towards its center

Slide 24

Using right hand rule which direction is the angular momentum?

Slide 25

In to the wall

Slide 26

A helicopters blades are rotating clockwise during a flight, if the tail rotor then breaks, what way will the body of the helicopter rotate?

Slide 27

Counterclockwise

Slide 28

Using the right hand rule, what would be the direction of the angular momentum of the below cylinder.

Slide 29

Up I

Slide 30

When trying to walk a balance beam why do you hold your arms out away from your sides?

Slide 31

To increase rotational inertia by moving part of your mass further away from the axis. In other words increasing your average radius

Slide 32

1 kg ?? 0 2 10 13 20

Slide 33

True or False RPM is a unit for rotational speed

Slide 34

True

Slide 35

In what direction is the centripetal force always pointed?

Slide 36

Inward, toward the center of the circular path

Slide 37

On the below rotating disk, which point has the highest linear speed? Rotational speed?

Slide 38

A) Star, covering the largest distance in the same amount of time B) All points have the same rotational speed

Slide 39

A 1000 Kg car and a 1500 kg car travel both travel at 15 m/s around a circular track. For which car will it be harder to stay in a circular path? (in other words which car will require more centripetal force to keep it on a circular path)

Slide 40

1500 kg car Has more mass, so has more inertia and is harder to keep in a circular path

Slide 41

Two 1000 kg cars are travelling on a circular track, one at 15 m/s and the other at 20 m/s, which one will require more centripetal force to keep it on its circular path?

Slide 42

20 m/s car, has largest tangential (linear) speed. Harder to keep object at a high speed in circular motion

Slide 43

Is Centripetal Force a quantity that is more relevant for something that is rotating or revolving?

Slide 44

Revolving

Slide 45

What is centrifugal force?

Slide 46

Fake force that gives the illusion of an outward force during circular motion Is actually just an object inertia

Slide 47

Where does an objects CoG have to be in order for it to balance?

Slide 48

Directly above its support base

Slide 49

When left to rotate freely, an object must rotate about an axis that goes through its _________.

Slide 50

Center of Gravity

Slide 51

Why is a lot of frozen ice on the deck of a big boat bad for the boat?

Slide 52

It raised the CoG and therefore makes it more likely to topple it is hit by a big wave