Rotational Motion 2

Rotational Motion 2

Multiple Choice

The see saw is balanced so the two torques are equal and opposite. Min is 75kg. Calculate Max’s mass.

• 100 kg

• 110 kg

• 113 kg

• 97 kg

Multiple Choice

Explain which has more rotational inertia a large 250 g metal can or a small 250g metal can.

• Large metal can, its mass is further from the centre

• Small metal can, its mass is closer to the centre

• They are the same as they have the same mass

Multiple Select

Explain why a ring is harder to spin than a solid disc (of same mass and radius)

• the ring has its mass further from the center (on average)

• the solid disc has its mass further from the center (on average)

• The ring has a smaller rotational inertia

• The ring has a larger rotational inertia

Multiple Select

Hannah has a bike wheel with a mass of 250 g and a radius of 74 cm.

Estimate the rotational inertia. What assumptions are you making?

• I = 0.14 kgm²

• assuming all mass is at the rim

• I = 0.19 kgm²

• assuming mass is evenly distributed

Multiple Choice

A bike wheel with a rotational inertia of 0.23 kgm² is initially moving with ω = 34 rads^-1. A force of 5.0 N is applied at 0.55 m from the centre of rotation until the wheel is brought to rest. What is the size of the angular acceleration and how long does it take to stop?

• α = 12 rads^-2 and t = 2.8 s

• α = 2.9 rads^-2 and t = 2.9 s

• α = 16 rads^-2 and t = 5.0 s