5.1 Rotational Kinematics

• Clockwise and speeding up
• Counterclockwise and speeding up
• Clockwise and Slowing down
• Counterclockwise and slowing down

The SI units for ω are

• rad

• rad/s

• rad/s²

• seconds

The SI units for α are

• rad

• rad/s

• rad/s²

• seconds

• - 8 rad/s²
• + 8 rad/s²
• -100 rad/s²
• -20 rad/s²

If the angular velocity of an object changes from 3 rad/s to 1 rad/s in 2 seconds, what is the object's angular acceleration?

• –1.5 rad/s^2
• –1 rad/s^2
• 1 rad/s^2
• 1.5 rad/s^2

An object rotates with an angular speed that varies with time, as shown in the graph. How can the graph be used to determine the magnitude of the angular acceleration α of the object? Justify your selection.

• Subtract the greatest value of the angular speed from the smallest value of the angular speed, because α=Δω.

• Determine the slope of the line from 0s to 2s, because the slope represents Δω/Δt.

• Determine the area bounded by the line and the horizontal axis from 0s to 2s, because α = 1/2ωΔt.

• The angular acceleration cannot be determined without knowing the rotational inertia of the object.

• 10 rad/sec

• 25 rad/sec

• 50 rad/sec

• 2 rad/sec