Physics Rotation Lesson

For a rotating rigid body, which of the following statements is NOT correct?

• All points along a rotating rigid body move with constant speed
• Points along a rotating body have velocities that continuously change directions
• Points along a rotating body move through the same angle in equal time intervals
• All of the answers are correct

A radian is all of the following EXCEPT

• A dimensionless quantity
• The ratio of arc length over radius
• The same as degrees
• The unit for rotational position

The minute hand of a clock goes from the ":00" position to the ":15" position in 15 minutes. What is the angular velocity of the clock hand?

• 6 degrees/minute
• π/30 radians/minute
• Both of the above
• Neither of the above

Does a bridge anchored resting on two pillars have any torque?

• No, it isn't moving
• Yes, but it is at equilibrium
• Yes, but it will soon break because of the torque
• No, Bridges can't have torque

The rotational equivalent to d (distance), v (velocity) and a (acceleration) are?

• m, m/s, m/s²
• θ, ω, α
• x, x/t, alphaα
• μ, Σ, τ

The center of mass is:

• the exact middle
• the heaviest part
• the point at which you can balance with one finger
• the idea that mass is concentrated throughout

How do you get the maximum torque?

• longer lever arm and less force at an acute angle
• shorter lever arm and less force perpendicularly
• shorter lever arm and more force perpendicularly
• longer lever arm and more force perpendicularly

A solid  metal bar is at rest on a horizontal frictionless surface. It is free to rotate about a vertical axis at the left end. The figures show forces of different magnitudes that are exerted on the bar at different locations. In which case does the bar's angular speed about the axis increase at the fastest rate?

• A
• B
• C
• D

Tags

NGSS.HS-PS2-1

In the diagram above, two masses, one with mass m, the other with mass M = 2m are resting on a uniform plank of length L that pivots at its midpoint. If the mass m is at the far end of the plank, how far away from the pivot should the mass M be to balance the plank in a horizontal position shown?

• L/2
• L/3
• L/4
• L/6

Tags

NGSS.HS-PS2-1

A person sits on a freely spinning lab stool that has no friction in its axle. When this person extends her arms,

• angular momentum is conserved, her moment of inertia increases and her angular speed decreases.
• angular momentum is conserved, her moment of inertia decreases and her angular speed increases.
• angular momentum increases, her moment of inertia increases and her angular speed increases.
• angular momentum decreases, her moment of inertia increases and her angular speed remains the same.