chapter 8

impulse variable and Unit

I n\*s

momentum variable and unit

p n\*s

what does theta mean

rotational displacement (rads)

what does omega mean

rotational velocity (radians/sec)

what does alpha mean?

rotational acc (radians/sec^2)

what does tile mean

torc (N\*m)

which is positive and negative when it comes to clockwise and counterclockwise

counterclockwise = positive

clockwise = negative

MO=

m(V)

kinetic energy is conserved means

momentum is conserved

MO Before = MO After comes from what

3rd law

MO Before = MO After means what

energy nor created nor destroyed

objects have some force and impulse comes from

3rd law

speed and mass determine outcomes

bog and fast control collision

A weight of 30 N is located 12 cm from the fulcrum on the beam of a simple balance. Determine the weight that should be placed at a point 5 cm from the fulcrum on the opposite side in order to balance the system.

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The weight that should be placed at a point 5 cm from the fulcrum on the opposite side is

72N

A coin rolls down an inclined plane, gaining speed as it rolls. Does the coin have rotational acceleration?

yes

How can an ice skater change his rotational velocity without involving any external torque?

by changing his shape

A tall crate has a higher center of gravity than a shorter crate. Which will have the greater tendency to tip over if we push near the top of the crate?

the taller crate

How does the rotational velocity of a boy sitting near the center of a rotating merry-go-round compare with that of a dog sitting near the edge of the same merry-go-round?

Both have the same rotational velocity.

You stand with your heels against a wall and bend ninety degrees forward at the waist.

You fall forward because your center of gravity moves ahead of your base of support.

Suppose a disk rotates through 19 revolutions in 5 seconds.

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What is its displacement in radians in this time?

119\.4 radians

A torque acting on a body tends to produce

rotational motion.

Torque in the metric system is measured in units of

N m

An object is moving in a horizontal circle, in a clockwise direction (as viewed from above). In which direction does its angular momentum vector point?

away from the viewer

In a stable stack of identical boards at the edge of a table, the center of gravity of the top board

must lie above the next lower board.

if you push directly on the handle of a closed door and it does not swing open, then

the net torque on the door must be zero.

A torque acting on a body tends to produce

rotational motion

Because the rotational inertia is higher, it is hardest in springboard diving to perform a forward somersault in

the straight position (no bending at knees or waist).

When one of the authors was a teenager, the rate of rotation for popular music records on a record player was 78 RPM.

 

Express the rotational velocity in rev/s

1\.3

A figure skater is spinning with her arms extended. She now pulls her arms close to her body. What happens?

Her rotational inertia decreases.

A hoop and a sphere have the same diameter and the same mass. Which one will have a larger rotational inertia?

the hoop

The bigger diameter gears on the rear wheel of a multi-speed bike allow the rider to

exert more torque on the wheel

A weight of 35 N is located at a distance of 8 cm from the fulcrum of a simple balance beam. At what distance from the fulcrum should a weight of 25 N be placed on the opposite side in order to balance the system?

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The required distance from the fulcrum to balance the system is

11\.2 cm

Which, if either, will produce the greater torque: a force applied at the end if a wrench handle (perpendicular to the handle) or an equal force applied in the same direction near the middle of the handle?

the force at the end of the wrench

An ice-skater is spinning counterclockwise about a vertical axis when viewed from above. What is the direction of her angular momentum vector?

upwards

Two objects have the same total mass, but object A has its mass concentrated closer to the axis of rotation than object B. Which object, if either, is easier to set into rotational motion?

object A

In what situation, if any, is angular momentum conserved??

only when the net torque is zero

The angular momentum of an isolated object can be changed only by

applying a torque.

A force of 25 N is applied at the end of a wrench handle that is 24 cm long. The force is applied in a direction perpendicular to the handle.

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What is the torque applied to the nut by the wrench? 

6 N