TOPIC 1 Review 1. Classify the levers in the illustrations as Class 1, Class 2, or Class 3. 2. How much work, in joules, must you do to lift an elephant weighing 60 000 N up 1.5 m onto the back of a truck? 3. You have found a ramp to lead up to the back of the truck. Will you and your team need to exert more, less, or the same forces as in question 2? 4. If you exert a force of 100 N on a hockey stick, and the stick exerts a force of 20 N on the puck, what is the mechanical advantage of the stick? 5. If the "effort arm" distance for the hockey stick in question 4 (between your "fulcrum" hand and your pushing hand) is 25 cm, how long is the stick? (Use your answer to question 4.) If your hand is pushing at a speed of 20 km/h, how fast will the puck move?

TOPIC 1 Review 1. Classify the levers in the illustrations as Class 1, Class 2, or Class 3. 2. How much work, in joules, must you do to lift an elephant weighing 60 000 N up 1.5 m onto the back of a truck? 3. You have found a ramp to lead up to the back of the truck. Will you and your team need to exert more, less, or the same forces as in question 2? 4. If you exert a force of 100 N on a hockey stick, and the stick exerts a force of 20 N on the puck, what is the mechanical advantage of the stick? 5. If the "effort arm" distance for the hockey stick in question 4 (between your "fulcrum" hand and your pushing hand) is 25 cm, how long is the stick? (Use your answer to question 4.) If your hand is pushing at a speed of 20 km/h, how fast will the puck move?

College Physics

11th Edition

ISBN:9781305952300

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter5: Energy

Section: Chapter Questions

Problem 27P: The chin-up is one exercise that can be used to strengthen the biceps muscle. This muscle can exert...

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The chin-up is one exercise that can be used to strengthen the biceps muscle. This muscle can exert a force of approximately 8.00 102 N as it contracts a distance of 7.5 cm in a 75-kg male.3 (a) How much work can the biceps muscles (one in each arm) perform in a single contraction? (b) Compare this amount of work with the energy required to lift a 75-kg person 40. cm in performing a chin-up. (c) Do you think the biceps muscle is the only muscle involved in performing a chin-up?
Give an example of something think of as work in everyday circumstances that is not work in the scientific sense. Is energy transferred or changed in form in your example? If so, explain how this without doing work.
. An elevator is able to raise 1,000 kg to a height of 40 m in 15 s. (a) How much work does the elevator do? (b) What is the elevator’s power output?
(a) How long would it takea 1.50105 -kg airplane with engines that produce 100 MW of power to reach a speed of 250 m,/s and an altitude of 12.0 km if air resistance were negligible? (b) If it actually takes 900 s, what is the power? (c) Given this power, what is the average force of air resistance if the airplane takes 1200 s? (Hint: You must find the distance the plane travels in 1200 s assuming constant acceleration.)
(a) How long will it take an 850-kg car with a useful power output of 40.0 hp (1hp=746W) to reach a speed of 15.0 m/s, neglecting friction? (b) How long will this acceleration take if the car also climbs a 3.00-m-high hill in the process?
Suppose a 350-g kookaburra (a large kingfisher bird) picks up a 75-g snake and raises it 2.5 m from the ground to a branch. (a) How much work did the bird do on the snake? (b) How much work did it do to raise its own center of mass to the branch?
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.
A block of stone weighs 500 newtons. It is 20m pushed up a slope. a. Neglecting friction, how much force is needed to push it up the incline at constant velocity? Show solutions and answer. b. How much work is done to push it up the incline? Show solutions and answer.
1. You push a 25 kg box up a 30 incline using a force of 210 N that is parallel to the ramp. The force due to kinetic friction is 65 N. a. Draw a free-body diagram of all the forces acting on the box (4 forces). Include the direction of displacement on your figure. b. How much work is done by EACH individual force as the box moves 1.9 m along the ramp? c. What is the net work done during this 1.9 m? d. How fast is the box moving after 1.9 m if it started from rest?
Suppose a 450 g kookaburra (a large kingfisher bird) picks up a 80 g snake and raises it 2.8 m from the ground to a branch. a. How much work (in J) did the bird do on the snake? b. How much work (in J) did it do to raise its own center of mass to the branch?
Two people use ropes to pull identical sofas up to their neighboring 5th floor apartments. One pulls up the sofa gradually in 100 seconds. The other pulls theirs up quickly in 20 seconds. The power output and the work done of the quick puller compares to that of the slow puller as a. work greater, power same b. work same, power greater c. work same, power same d. work greater, power greater
A. Suppose you lift a 15 kg box by a height of 1.0 m. How much work do you do in lifting the box? Express your answer using two significant figures. B. Instead of lifting the box straight up, suppose you push it up a 1.0-m-high ramp that makes a 30 ∘ degree angle with the horizontal, as shown in (Figure 1). Being clever, you choose a ramp with no friction. How much force is required to push the box straight up the slope at a constant speed? Express your answer using two significant figures. C. How long is the ramp? Express your answer using two significant figures. D. Use your force and distance results to calculate the work you do in pushing the box up the ramp. Express your answer using two significant figures.