# Kinetic energy and work problem

• J-dizzal
In summary, the conversation discusses a block of ice sliding down a frictionless ramp while an ice worker pulls on it with a force of 54.0 N. As the block slides down a distance of 0.400 m, its kinetic energy increases by 80.0 J. The question then asks how much greater the kinetic energy would have been if the rope had not been attached to the block. The correct answer is 21.6 J, which is the difference between the kinetic energy with the rope attached (101.6 J) and without the rope (80.0 J).
J-dizzal

## Homework Statement

In the figure here, a block of ice slides down a frictionless ramp at angle θ=55.0 ˚ while an ice worker pulls on the block (via a rope) with a force that has a magnitude of 54.0 N and is directed up the ramp. As the block slides down through distance d = 0.400 m along the ramp, its kinetic energy increases by 80.0 J. How much greater would its kinetic energy have been if the rope had not been attached to the block?

http://edugen.wileyplus.com/edugen/courses/crs7165/art/qb/qu/c07/fig_7_C.gif

## Homework Equations

K=1/2 mv2, w=Fd, http://edugen.wileyplus.com/edugen/courses/crs7165/halliday9781118230725/c07/math/math080.gif, http://edugen.wileyplus.com/edugen/courses/crs7165/halliday9781118230725/c07/math/math082.gif

## The Attempt at a Solution

The work done in the positive x dir is -21.6 because the box is sliding down, if the kinetic energy is 80J then 21.6J+80J=101.6J is the total. But this is not right.
http://i1164.photobucket.com/albums/q562/falsovero/20150630_163254_zps9et5lfe6.jpg [/B]

Last edited by a moderator:
J-dizzal said:

## Homework Statement

In the figure here, a block of ice slides down a frictionless ramp at angle θ=55.0 ˚ while an ice worker pulls on the block (via a rope) with a force that has a magnitude of 54.0 N and is directed up the ramp. As the block slides down through distance d = 0.400 m along the ramp, its kinetic energy increases by 80.0 J. How much greater would its kinetic energy have been if the rope had not been attached to the block?

http://edugen.wileyplus.com/edugen/courses/crs7165/art/qb/qu/c07/fig_7_C.gif

## Homework Equations

K=1/2 mv2, w=Fd, http://edugen.wileyplus.com/edugen/courses/crs7165/halliday9781118230725/c07/math/math080.gif, http://edugen.wileyplus.com/edugen/courses/crs7165/halliday9781118230725/c07/math/math082.gif

## The Attempt at a Solution

The work done in the positive x dir is -21.6 because the box is sliding down, if the kinetic energy is 80J then 21.6J+80J=101.6J is the total. But this is not right.
http://i1164.photobucket.com/albums/q562/falsovero/20150630_163254_zps9et5lfe6.jpg [/B]
What is the correct answer?

"How much greater would its kinetic energy have been if the rope had not been attached to the block?"​

Last edited by a moderator:
its would be 101.6 - 80. would be the difference between the the work with the 54N and without?

"How much greater would its kinetic energy have been if the rope had not been attached to the block?"​
thanks i need to work on this, it gets me often.

## 1. What is kinetic energy and how is it different from work?

Kinetic energy is the energy an object possesses due to its motion. It is different from work because work is the transfer of energy from one object to another, while kinetic energy is the energy an object has on its own due to its motion.

## 2. How do you calculate kinetic energy?

Kinetic energy can be calculated using the formula KE = 1/2 * m * v^2, where m is the mass of the object and v is its velocity.

## 3. Can kinetic energy be negative?

No, kinetic energy cannot be negative. It is a measure of an object's motion and is always a positive value.

## 4. How is kinetic energy related to potential energy?

Kinetic energy and potential energy are two forms of energy that can be converted into each other. An object's potential energy, such as gravitational potential energy, can be converted into kinetic energy as the object falls. Similarly, the kinetic energy of an object can be converted into potential energy, such as when a ball is thrown upward and gains potential energy as it rises.

## 5. How is kinetic energy affected by mass and velocity?

The kinetic energy of an object is directly proportional to its mass and the square of its velocity. This means that an object with a higher mass or velocity will have a greater kinetic energy compared to an object with a lower mass or velocity.

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