A sledder sits stationary at the top of a 42-m tall hill. The child and the sled

Question

A sledder sits stationary at the top of a 42-m tall hill. The child and the sled have a combined mass of 74 kg. a) What is the initial gravitational potential energy of the child and sled? b) The sled begins moving down the hill. When he passes his mother at point B, he is 14 m above the bottom of the hill. What is the gravitational energy at this point? c) If the work done against friction between the top of the hill and point B is 2400 J, what is the kinetic energy of the child and sled as they pass his mother? d) How fast is the sled moving at this point? A 780-kg roller coaster begins from rest at the top of a 62-m tall hill. a) What is the gravitational potential energy of the roller coaster at the top of the hill? b) At the bottom of the hill, the coaster is moving at 30 m/s. What is the kinetic energy of the roller coaster at this point? c) How much work was done by air resistance and friction on the way down the hill? A mass on a spring oscillates through 20 cycles in 8 seconds. a) What is the frequency of the motion? b) What is the period of the motion?

Explanation / Answer

Multiple questions Allowed to answer only 1 question at a time According to the chegg guidelines.

11) No of cycles = 20 cycles t = 8.0 seconds

Frequency = No of oscillations / time = 20 /8 = 2.5 Hz =====Part a)

Period = 1/ F = 1/ 2.5 Hz = 0.400 s ===================Part b)

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