A 56.6-kg skateboarder starts out with a speed of 2.28 m/s. He does 96.5 J of work on himself by pushing with his feet against the ground. In addition, friction does-298 J of work on him. In both cases, the forces doing the work are non-conservative. The final speed of the skateboarder is 8.16 m/s. (a) Calculate the change (PE-PEo) in the gravitational potential energy. (b) How much has the vertical height of the skater changed? Give the absolute value. (a) Number i (b) Number i Units Units

A 56.6-kg skateboarder starts out with a speed of 2.28 m/s. He does 96.5 J of work on himself by pushing with his feet against the ground. In addition, friction does-298 J of work on him. In both cases, the forces doing the work are non-conservative. The final speed of the skateboarder is 8.16 m/s. (a) Calculate the change (PE-PEo) in the gravitational potential energy. (b) How much has the vertical height of the skater changed? Give the absolute value. (a) Number i (b) Number i Units Units

Name: View PoliciesCurrent Attempt in ProgressA 56.6-kg skateboarder starts
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Description: View PoliciesCurrent Attempt in ProgressA 56.6-kg skateboarder starts out with a speed of 2.28 m/s. He does 96.5 J of work on himself by pushing with his feet against theground. In addition, friction does -298 J of work on him. In both cases, the fo

Physics for Scientists and Engineers

10th Edition

ISBN:9781337553278

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter7: Energy Of A System

Section: Chapter Questions

Problem 28P: Review. A 7.80-g bullet moving at 575 m/s strikes the hand of a superhero, causing the hand to move...

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Integrated Concepts (a) Calculate the force the woman in Figure 7.46 exerts to do a push-up at constant speed, taking all data to be known to three digits. (b) How much work does she do if her center of mass rises 0.240 m? (c) What is her useful power output if she does 25 push-ups in 1 min? (Should work done lowering her body be included? See the discussion of useful work in Work, Energy, and Power in Humans. Figure 7.46 Forces involved in doing push-ups. The woman's weight acts as a force exerted downward on her center of gravity (CG).
Give an example of a situation in which there is a force and a displacement, but the force does no work. Explain why it does no work.
Calculate the work done by an 85.0-kg man who pushes a crate 4.00 m up along a ramp that makes an angle of 20.0° with the horizontal. (See Figure 7.35.) He exerts a force of 500 N on the crate parallel to the ramp and moves at a constant speed. Be certain to include the work he does on the crate and on his body to get up the ramp. Figure 7.35 A man pushes a crate up a ramp.
Alex and John are loading identical cabinets onto a truck. Alex lifts his cabinet straight up from the ground to the bed of the truck, whereas John slides his cabinet up a rough ramp to the truck. Which statement is correct about the work done on the cabinet-Earth system? (a) Alex and John do the same amount of work, (b) Alex does more work than John, (c) John does more work than Alex, (d) None of those statements is necessarily true because the force of friction is unknown, (e) None of those statements is necessarily true because the angle of the incline is unknown.
In Figure 5.5 (a)-(d), a block moves to the right in the positive x-direction through the displacement x while under the influence of a force with the same magnitude F. Which of the following is the correct order of the amount of work done by the force F, from most positive to most negative? (a) d, c, a, b (b) c, a, b, d (c) c, a, d, b
Give an example of a situation in which there is a force and a displacement, but the force does no work. Explain why it does no work.
a shopper in a supermarket pushes a cart with a force of 35 N directed at an angle of 25 below the horizontal. The force is just sufficient to overcome various frictional forces, so the cart moves at constant speed, (a) Find the work done by the shopper as she moves down a 50.0-m length aisle, (b) What is the net work done on the cart? Why? (c) The shopper goes down the next aisle, pushing horizontally and maintaining the same speed as before. If the work done by frictional forces doesnt change, would the shoppers applied force be larger, smaller, or the same? What about the work done on the cart by the shopper?
a shopper in a supermarket pushes a cart with a force of 35 N directed at an angle of 25 below the horizontal. The force is just sufficient to overcome various frictional forces, so the cart moves at constant speed, (a) Find the work done by the shopper as she moves down a 50.0-m length aisle, (b) What is the net work done on the cart? Why? (c) The shopper goes down the next aisle, pushing horizontally and maintaining the same speed as before. If the work done by frictional forces doesnt change, would the shoppers applied force be larger, smaller, or the same? What about the work done on the cart by the shopper?
Two toboggans (with riders) of the same mass are at rest on top of a steep hill. As they slide down the hill, toboggan A takes a straight path down the slope while toboggan B winds back and forth along a more gently sloping path. Toboggan A makes the trip in half the time of toboggan B. (a) Compare the work done by gravity on each toboggan. (b) Compare the average power delivered by gravity on the two toboggans.
A worker pushing a 35.0-kg wooden crate at a constant speed for 12.0 m along a wood floor does 350 J of work by applying a constant horizontal force of magnitude F0 on the crate. (a) Determine the value of F0. (b) If the worker now applies a force greater than F0, describe the subsequent motion of the crate. (c) Describe what would happen to the crate if the applied force is less than F0.
What does work on a shuffleboard puck as it slides to rest? Why is the board dusted, and how does this affect work?
Mark and David are loading identical cement blocks onto Davids pickup truck. Mark lifts his block straight up from the ground to the truck, whereas David slides his block up a ramp on massless, frictionless rollers. Which statement is true? (a) Mark does more work than David. (b) Mark and David do the same amount of work. (c) David does more work than Mark. (d) None of these statements is necessarily true because the angle of the incline is unknown. (e) None of these statements is necessarily true because the mass of one block is not given.