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11/8 Rotational Energy

11/8 Rotational Energy. Today: Rotational Energy Examples HW: 11/8 HW Handout “Skateboard” due Thursday 11/14 Exam 3: Thursday, 11/14 5-7 in 116, 6-8 in 114, Email me if other time needed Monday holiday-no lab next week!. Systems of objects.

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11/8 Rotational Energy

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  1. 11/8 Rotational Energy • Today: Rotational Energy Examples • HW: 11/8 HW Handout “Skateboard” due Thursday 11/14 • Exam 3: Thursday, 11/145-7 in 116, 6-8 in 114, Email me if other time needed • Monday holiday-no lab next week!

  2. Systems of objects A Skateboard made of 4 wheels (disks, 1kg each) and a board (2kg). Rolls without slipping at 1m/s So 1/4 in rotation and 3/4 in translation Total Energy = 4J Sort the total energy into buckets: KET = Board and Wheels = 3J KER = Just Wheels KER of disk = 1/2 KET of disk KET of disk = 0.5J so KER disk = 0.25J KER = 1J for all 4 wheels

  3. R R T T g g S S Systems of objects A Skateboard made of 4 wheels (disks, 1kg each) and a board (2kg). Rolls without slipping at 1m/s So 1/4 in rotation and 3/4 in translation How fast would the skateboard be moving if it rolled from rest without slipping down a ramp, losing 4m of altitude? Energy still split 1/4 : 3/4 0 0 0 0 0 KER = 60J Top of ramp Bottom of ramp KET = 180J PE = 240J 1/2mv2 = 180J v = 7.75m/s

  4. ? ? ? 0 R R T T g g S S Pulley and Block We have a block with mass 3m hanging from a ring (pulley) of mass m and radius r, which rides on a frictionless axle. The system is released from rest. Axle Energy of the system m top 0 0 0 PE is for the block only. Where is the energy?How is it split? bottom 0 1/4 : 3/4 3 parts T and 1 part R 3m v = 0 How do the velocities of the block and ring compare? How do the velocities of the block and string compare? h vB = vString = vR not slipping! v = ? How do the masses of the block and ring compare? How does the KER of the ring compare to the KET of the block?

  5. ? ? ? 6gh v = R R T T g g S S 4 0 0 0 Pulley and Block We have a block with mass 3m hanging from a ring (pulley) of mass m and radius r, which rides on a frictionless axle. The system is released from rest. Axle m PE is for the block only. Where is the energy?How is it split? 0 0 1/4 : 3/4 3/4mgh = 1/2mv2 3m v = 0 h v = ?

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