Concept Items
9.1 Work, Power, and the Work–Energy Theorem
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No, because the work-energy theorem states that work done on an object is equal to the change in kinetic energy, and change in KE requires a change in velocity. It is assumed that mass is constant.
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No, because the work-energy theorem states that work done on an object is equal to the sum of kinetic energy, and the change in KE requires a change in displacement. It is assumed that mass is constant.
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Yes, because the work-energy theorem states that work done on an object is equal to the change in kinetic energy, and change in KE requires a change in velocity. It is assumed that mass is constant.
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Yes, because the work-energy theorem states that work done on an object is equal to the sum of kinetic energy, and the change in KE requires a change in displacement. It is assumed that mass is constant.
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Work is defined as the ratio of the force over the distance.
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Work is defined as the sum of the force and the distance.
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Work is defined as the square of the force over the distance.
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Work is defined as the product of the force and the distance.
A book with a mass of 0.30 kg falls 2 m from a shelf to the floor. This event is described by the work–energy theorem: Explain why this is enough information to calculate the speed with which the book hits the floor.
- The mass of the book, m, and distance, d, are stated. F is the weight of the book mg . v1 is the initial velocity and v2 is the final velocity. The final velocity is the only unknown quantity.
- The mass of the book, m, and distance, d, are stated. F is the weight of the book mg . v1 is the final velocity and v2 is the initial velocity. The final velocity is the only unknown quantity.
- The mass of the book, m, and distance, d, are stated. F is the weight of the book mg . v1 is the initial velocity and v2 is the final velocity. The final velocity and the initial velocities are the only unknown quantities.
- The mass of the book, m, and distance, d, are stated. F is the weight of the book mg . v1 is the final velocity and v2 is the initial velocity. The final velocity and the initial velocities are the only unknown quantities.
9.2 Mechanical Energy and Conservation of Energy
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While going up, the person’s KE would change to PE. While coming down, the person’s PE would change to KE.
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While going up, the person’s PE would change to KE. While coming down, the person’s KE would change to PE.
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While going up, the person’s KE would not change, but while coming down, the person’s PE would change to KE.
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While going up, the person’s PE would change to KE, but while coming down, the person’s KE would not change.
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v = h
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v = \sqrt{2h}
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v = gh
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v = \sqrt{2gh}
The starting line of a cross country foot race is at the bottom of a hill. Which form(s) of mechanical energy of the runners will change when the starting gun is fired?
- Kinetic energy only
- Potential energy only
- Both kinetic and potential energy
- Neither kinetic nor potential energy
9.3 Simple Machines
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It reduces the input force and the output force.
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It reduces the input force and increases the output force.
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It increases the input force and reduces the output force.
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It increases the input force and the output force.
Which type of simple machine is a knife?
- A ramp
- A wedge
- A pulley
- A screw