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occurred Apr 30, 2017 at 11:16

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edited Apr 30, 2017 at 6:18

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A rock is lifted for a certain time by a force $F$ that is greater in magnitude than the rock’s weight W$W$. The change in kinetic energy of the rock during this time is equal to the

A. work done by the net force ($F - W$)
B. work done by $F$ alone
C. work done by $W$ alone
D. difference in the potential energy of the rock before and after this time.

The correct answer is A. I understand why this is so: The work–energy theorem states that the net work done on an object is equal to its change in kinetic energy.

What I’m having trouble understanding is why answer choice D is incorrect. If a rock is falling from a given height, the rock’s change in kinetic energy (which goes from $0$ to $\frac{1}{2}mv^2$) is equal to its change in potential energy (which goes from $mgh$ to $0$). What is different about the scenario presented in the problem that doesn’t make D correct?

A rock is lifted for a certain time by a force $F$ that is greater in magnitude than the rock’s weight W. The change in kinetic energy of the rock during this time is equal to the

A. work done by the net force ($F - W$)
B. work done by $F$ alone
C. work done by $W$ alone
D. difference in the potential energy of the rock before and after this time.

The correct answer is A. I understand why this is so: The work–energy theorem states that the net work done on an object is equal to its change in kinetic energy.

What I’m having trouble understanding is why answer choice D is incorrect. If a rock is falling from a given height, the rock’s change in kinetic energy (which goes from $0$ to $\frac{1}{2}mv^2$) is equal to its change in potential energy (which goes from $mgh$ to $0$). What is different about the scenario presented in the problem that doesn’t make D correct?

A rock is lifted for a certain time by a force $F$ that is greater in magnitude than the rock’s weight $W$. The change in kinetic energy of the rock during this time is equal to the

A. work done by the net force ($F - W$)
B. work done by $F$ alone
C. work done by $W$ alone
D. difference in the potential energy of the rock before and after this time.

The correct answer is A. I understand why this is so: The work–energy theorem states that the net work done on an object is equal to its change in kinetic energy.

What I’m having trouble understanding is why answer choice D is incorrect. If a rock is falling from a given height, the rock’s change in kinetic energy (which goes from $0$ to $\frac{1}{2}mv^2$) is equal to its change in potential energy (which goes from $mgh$ to $0$). What is different about the scenario presented in the problem that doesn’t make D correct?

Setting task in quote block, more concise title, formatting equations, minor stuff.

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edited Apr 30, 2017 at 5:52

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6.4k
2
27
47

A Change of kinetic energy of a rock is lifted for a certain time by a force F greater than it'sits weight. What is the change in KE of the rock during this time?

A rock is lifted for a certain time by a force F that is greater in magnitude than the rock's weight W. The change in kinetic energy of the rock during this time is equal to the

A rock is lifted for a certain time by a force $F$ that is greater in magnitude than the rock’s weight W. The change in kinetic energy of the rock during this time is equal to the

(A) work done by the net force (F - W)
(B) work done by F alone
(C) work done by W alone
(D) difference in the potential energy of the rock before and after this time.

A. work done by the net force ($F - W$)
B. work done by $F$ alone
C. work done by $W$ alone
D. difference in the potential energy of the rock before and after this time.

The correct answer is A A. I understand why this is so: the work-energyThe work–energy theorem states that the net work done on an object is equal to its change in kinetic energy.

What I'mI’m having trouble understanding is why answer choice D is incorrect. If a rock is falling from a given height, the rock'srock’s change in kinetic energy (which goes from 0$0$ to 1/2mv^2$\frac{1}{2}mv^2$) is equal to its change in potential energy (which goes from mgh$mgh$ to 0$0$). What is different about the scenario presented in the problem that doesn'tdoesn’t make D correct?

A rock is lifted for a certain time by a force F greater than it's weight. What is the change in KE of the rock during this time?

A rock is lifted for a certain time by a force F that is greater in magnitude than the rock's weight W. The change in kinetic energy of the rock during this time is equal to the

(A) work done by the net force (F - W)
(B) work done by F alone
(C) work done by W alone
(D) difference in the potential energy of the rock before and after this time.

The correct answer is A. I understand why this is so: the work-energy theorem states that the net work done on an object is equal to its change in kinetic energy.

What I'm having trouble understanding is why answer choice D is incorrect. If a rock is falling from a given height, the rock's change in kinetic energy (which goes from 0 to 1/2mv^2) is equal to its change in potential energy (which goes from mgh to 0). What is different about the scenario presented in the problem that doesn't make D correct?

Change of kinetic energy of a rock lifted by a force greater than its weight

A rock is lifted for a certain time by a force $F$ that is greater in magnitude than the rock’s weight W. The change in kinetic energy of the rock during this time is equal to the

A. work done by the net force ($F - W$)
B. work done by $F$ alone
C. work done by $W$ alone
D. difference in the potential energy of the rock before and after this time.

The correct answer is A. I understand why this is so: The work–energy theorem states that the net work done on an object is equal to its change in kinetic energy.

What I’m having trouble understanding is why answer choice D is incorrect. If a rock is falling from a given height, the rock’s change in kinetic energy (which goes from $0$ to $\frac{1}{2}mv^2$) is equal to its change in potential energy (which goes from $mgh$ to $0$). What is different about the scenario presented in the problem that doesn’t make D correct?