A student eats a dinner rated at 2 000 Calories. He wishes to do an equivalent amount of work in the gymnasium by lifting a 50.0-kg barbell. How many times must he raise the barbell to expend this much energy? Assume he raises the barbell 2.00 m each time he lifts it and he regains no energy when he lowers the barbell.

As h Ramp #1 Ramp #2 A block (4 kg) starts from rest and slides down a frictionless ramp #1 of height 7 m. The block then slides a horizontal distance of 1.5 m on a rough surface with kinetic coefficient of friction Hk = 0.5. Next, it slides back up another frictionless ramp #2. Find the following numerical energy values: Initial gravitational potential energy on Ramp #1: U1G = Submit Answer Tries 0/2 Kinetic energy at bottom of Ramp #1 before traveling across the rough surface: K = Submit Answer Tries 0/2 Magnitude of Heat dissipated by friction after traveling across the rough surface: fAs = J Submit Answer Tries 0/2 Kinetic energy at bottom of Ramp #2 after traveling across the rough surface: K = J Submit Answer Tries 0/2 Final gravitational potential energy on Ramp #2 after momentarily stopping: U2G = Submit Answer Tries 0/2 The block then slides back down Ramp #2 and across the rough surface to Ramp #1 again. Find the following numerical energy values: Kinetic energy at bottom of…

Kangaroos have very stout tendons in their legs that can be used to store energy. When a kangaroo lands on its feet, the tendons stretch, transforming kinetic energy of motion to elastic potential energy. Much of this energy can be transformed back into kinetic energy as the kangaroo takes another hop. The kangaroo’s peculiar hopping gait is not very efficient at low speeds but is quite efficient at high speeds. as shown the energy cost of human and kangaroo locomotion. The graph shows oxygen uptake (in mL/s) per kg of body mass, allowing a direct comparison between the two species. For humans, the energy used per second (i.e., power) is proportional to the speed. That is, the human curve nearly passes through the origin, so running twice as fast takes approximately twice as much power. For a hopping kangaroo, the graph of energy use has only a very small slope. In other words, the energy used per second changes very little with speed. Going faster requires very little additional…

On a playground slide, a child has potential energy PE = 450.0 J at the top of the slide. Thechild’s mass is 25.0 kg. (For simplicity, take the value of g to be 10.0 m/s2 in this problem.) When the child slides down to the bottom of the slide, her KE = 300.0 J. a) What was the height of the slide?b) How much was the work done by friction?c) How fast was the child moving when she reached the middle of the slide? (Assume that thework done by friction is half of what you get in (b). Note that the PE2 is not zero this time.)

A 4 kg block is initially sliding up a 30° incline at 6 m/s. It slides 3 m along the surface before coming to rest.  Gravity did ____ J of work on the block during this segment of motion.   A 4 kg block is initially sliding up a 30° incline at 6 m/s. It slides 3 m along the surface before coming to rest.  Kinetic friction did ____ J of work on the block during this segment of motion.

A student uses a wheelchair to get around campus, which she travels to on a public bus. She boards the bus using a motorized lift attached near the bus door. The electric lift motor uses 1.4 kilojoules of energy to raise the student and wheelchair from the sidewalk to the level of the bus interior, a total displacement of 0.75 meters. If the mass of the wheelchair is 20 kilograms and the mass of the student and her belongings is 60 kilograms, what is the efficiency of the motor(Estimate g as 10 m/s2.)