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9. Work & Energy

Net Work & Work-Energy Theorem

9. Work & Energy

Net Work & Work-Energy Theorem

Guided videos.

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Calculating Net Work

The Work-Energy Theorem

Net Work & Constant Speed

Additional 2 creators.

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Anderson Video - Work Lowering an Object

Professor Anderson

Work Energy Principle

Bozeman Science

Work done by a constant force on a brick, and final speed. Includes friction.

Calculating work done by drag in a vertical fall. Work done by gravity and drag given final speed.

Calculating total work and final speed when the force is constant over time.

Calculating net work and final speed, with applied force at an angle and friction.

Physics Lesson: Kinetic Energy and Work, Conservation Part 3 Help Lesson

Physicshelp Canada

Physics Lesson: Kinetic Energy and Work, Conservation Part 2 Help Lesson

Physicshelp Canada

Work - Kinetic Energy Theorem

Work: Introduction

Showing 10 of 10 videos

Practice this topic

Multiple Choice

You pull a 3kg box on a flat surface. The coefficient of kinetic friction is 0.6. When you pull the box horizontally through a distance of 10m, it accelerates at 2m/s2. Find the net work on the box.

Has a video solution.

Multiple Choice

To pull a 51 kg crate across a rough floor, a worker applies a force of 100 N, directed 37°above the horizontal. The coefficient of friction is 0.16. If the crate moves 3.0 m, what is the total work done on the crate?

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Multiple Choice

A box slides across the floor with an initial speed of 3.5m/s. If the coefficient of kinetic friction is 0.15, how far will the box slide before stopping completely?

Has a video solution.

Multiple Choice

10 kg

crate a shove across a horizontal floor. When the crate left his hands, it was moving

5.0 m / s

. If the coefficient of kinetic friction between the crate and the floor is 0.32, how far will the crate slide? Use energy concepts to solve this problem.

Textbook Question

You throw a 3.00-N rock vertically into the air from ground level. You observe that when it is 15.0 m above the ground, it is traveling at 25.0 m/s upward. Use the work–energy theorem to find (b) its maximum height.

Has a video solution.

Textbook Question

A 1.50-kg book is sliding along a rough horizontal surface. At point A it is moving at 3.21 m/s, and at point B it has slowed to 1.25 m/s. (a) How much work was done on the book between A and B?

Has a video solution.

Textbook Question

You throw a 3.00-N rock vertically into the air from ground level. You observe that when it is 15.0 m above the ground, it is traveling at 25.0 m/s upward. Use the work–energy theorem to find (a) the rock's speed just as it left the ground

Has a video solution.

Textbook Question

An 8.0 kg crate is pulled 5.0 m up a 30° incline by a rope angled 18 ° above the incline. The tension in the rope is 120 N, and the crate's coefficient of kinetic friction on the incline is 0.25. (b) What is the increase in thermal energy of the crate and incline?

Has a video solution.

Textbook Question

A 2.0 kg particle moving along the x-axis experiences the force shown in FIGURE EX9.22. The particle's velocity is 3.0 m/s at x = 0m . At what point on the x-axis does the particle have a turning point?

Has a video solution.

Textbook Question

A red ball has a mass of 250 g. A constant force pushes the red ball horizontally and launches it at a speed of 15 m/s . The same force pushes a green ball through the same distance, launching it at 25 m/s. What is the mass of the green ball?

Has a video solution.

Textbook Question

A pitcher accelerates a 150 g baseball from rest to 35 m/s. How much work does the pitcher do on the ball?

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Textbook Question

A horizontal spring with spring constant 85 N/m extends outward from a wall just above floor level. A 1.5 kg box sliding across a frictionless floor hits the end of the spring and compresses it 6.5 cm before the spring expands and shoots the box back out. How fast was the box going when it hit the spring?

Has a video solution.

Textbook Question

A ball shot straight up with kinetic energy K₀ reaches height h. What height will it reach if the initial kinetic energy is doubled?

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Textbook Question

A 55 kg softball player slides into second base, generating 950 J of thermal energy in her legs and the ground. How fast was she running?

Has a video solution.

Textbook Question

A baggage handler throws a 15 kg suitcase along the floor of an airplane luggage compartment with a speed of 1.2 m/s. The suitcase slides 2.0 m before stopping. Use work and energy to find the suitcase's coefficient of kinetic friction on the floor.

Has a video solution.

Textbook Question

Justin, with a mass of 30 kg, is going down an 8.0-m-high water slide. He starts at rest, and his speed at the bottom is 11 m/s. How much thermal energy is created by friction during his descent?

Has a video solution.

Textbook Question

A 50 kg ice skater is gliding along the ice, heading due north at 4.0 m/s. The ice has a small coefficient of static friction, to prevent the skater from slipping sideways, but μₖ = 0. Suddenly, a wind from the northeast exerts a force of 4.0 N on the skater. (a) Use work and energy to find the skater's speed after gliding 100 m in this wind.

Has a video solution.

Textbook Question

A 737-800 jet airliner has twin engines, each with 105 kN thrust. A 78,000 kg jet reaches a takeoff speed of 70 m/s in a distance of 1100 m. (b) What is the increase in thermal energy due to rolling friction and air drag?

Has a video solution.

Textbook Question

A horizontal spring with spring constant 250 N/m is compressed by 12 cm and then used to launch a 250 g box across the floor. The coefficient of kinetic friction between the box and the floor is 0.23. What is the box's launch speed?

Has a video solution.

Textbook Question

(a) How much work does an elevator motor do to lift a 1000 kg elevator a height of 100 m?

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Textbook Question

Susan's 10 kg baby brother Paul sits on a mat. Susan pulls the mat across the floor using a rope that is angled 30° above the floor. The tension is a constant 30 N and the coefficient of friction is 0.20. Use work and energy to find Paul's speed after being pulled 3.0 m.

Has a video solution.

Textbook Question

FIGURE EX9.20 is the force-versus-position graph for a particle moving along the x-axis. Determine the work done on the particle during each of the three intervals 0–1 m, 1–2 m, and 2–3 m.

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Textbook Question

A horizontal spring with spring constant 750 N/m is attached to a wall. An athlete presses against the free end of the spring, compressing it 5.0 cm. How hard is the athlete pushing?

Has a video solution.

Textbook Question

The cable of a crane is lifting a 750 kg girder. The girder increases its speed from 0.25 m/s to 0.75 m/s in a distance of 3.5 m. (a) How much work is done by gravity?

Has a video solution.

Textbook Question

A 50 kg ice skater is gliding along the ice, heading due north at 4.0 m/s. The ice has a small coefficient of static friction, to prevent the skater from slipping sideways, but μₖ = 0. Suddenly, a wind from the northeast exerts a force of 4.0 N on the skater. (b) What is the minimum value of μₛ that allows her to continue moving straight north?

Textbook Question

A pile driver lifts a 250 kg weight and then lets it fall onto the end of a steel pipe that needs to be driven into the ground. A fall from an initial height of 1.5 m drives the pipe in 35 cm. What is the average force that the weight exerts on the pipe?

Textbook Question

CALC A 2.6 kg block is attached to a horizontal rope that exerts a variable force Fx=(20−5x) N, where x is in m. The coefficient of kinetic friction between the block and the floor is 0.25. Initially the block is at rest at x=0 m . What is the block's speed when it has been pulled to x=4.0 m?

Has a video solution.

Textbook Question

The maximum energy a bone can absorb without breaking is surprisingly small. Experimental data show that a leg bone of a healthy, 60 kg human can absorb about 200 J. From what maximum height could a 60 kg person jump and land rigidly upright on both feet without breaking his legs? Assume that all energy is absorbed by the leg bones in a rigid landing.

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Textbook Question

A 20 kg child is on a swing that hangs from 3.0-m-long chains. What is her maximum speed if she swings out to a 45 degree angle?

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Textbook Question

In a hydroelectric dam, water falls 25 m and then spins a turbine to generate electricity. (a) What is (delta)Ug of 1.0 kg of water?

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Textbook Question

A cable with 20.0 N of tension pulls straight up on a 1.50 kg block that is initially at rest. What is the block's speed after being lifted 2.00 m? Solve this problem using work and energy.

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Textbook Question

A 1500 kg car traveling at 10 m/s suddenly runs out of gas while approaching the valley shown in FIGURE EX10.11. The alert driver immediately puts the car in neutral so that it will roll. What will be the car's speed as it coasts into the gas station on the other side of the valley? Ignore rolling friction.

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Textbook Question

A pendulum is made by tying a 500 g ball to a 75-cm-long string. The pendulum is pulled 30 degree to one side, then released. What is the ball's speed at the lowest point of its trajectory?

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Textbook Question

A 55 kg skateboarder wants to just make it to the upper edge of a 'quarter pipe,' a track that is one-quarter of a circle with a radius of 3.0 m. What speed does he need at the bottom?

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Textbook Question

A system of two objects has (delta)Ktot = 7J and (delta)U = -5J. (a) How much work is done by interaction forces?

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