# Finding the Work Done by Friction w/out Friction

• Internetwork
In summary, the work done by friction between the baseball player and the ground is -1700 J. This can also be calculated by finding the change in kinetic energy of the player. The coefficient of kinetic friction can be determined by using the equation F = μN. The player's mass, initial velocity, and final velocity were used to calculate the work done by friction, and the answer was found to be -169 J. However, upon further inspection, it was discovered that the correct answer should be -1700 J, indicating that the player's initial velocity was incorrect. After correcting this error, the final answer was found to be -1690 J, which is approximately equal to -1700 J.
Internetwork
I feel like I'm missing some obvious or simple piece but I can't seem to figure out the first part. If I can get the first part, the second part is easy.

1. Homework Statement

An 80-kg baseball player running at 6.5 m/s goes into a slide 3.0 m from second base. He comes to rest just as he touches the bag. What is the work done by friction? What is the coefficient of kinetic friction between the player and the ground?

W = F * d
W = ΔK
F = μN

## The Attempt at a Solution

This seemed straight forward. I calculated the kinetic energy to get the overall work:
W = Kf - Ki = 1/2mv_f^2 - 1/2mv_i^2 = -169 J
This should be the same work as the friction but I've been told the correct answer should be -1700 J. Am I wrong about something here?

Last edited:
Check your arithmetic.

Bystander said:
Check your arithmetic.

m = 80kg
v_i = 6.5m/s
v_f = 0

1/2(80)(0)^2 - 1/2(80)(6.5)^2 =
0 - 1/2(80)(42.25) =
0 - 1/2(338) =
0 - 169 = -169

Same answer.

Check it again --- it's glaring at me with big red eyes.

Wow! How did I miss that twice!

1/2(80)(0)^2 - 1/2(80)(6.5)^2 =
0 - 1/2(80)(42.25) =
0 - 1/2(3380) =
0 - 1690 = -1690 ≈ -1700

## 1. What is the definition of "work" in scientific terms?

In physics, work is defined as the application of a force over a distance, resulting in the displacement of an object in the direction of the force.

## 2. How is work calculated when there is no friction involved?

When there is no friction involved, the work done is equal to the force applied multiplied by the distance traveled in the direction of the force. This is known as the formula for work: W = Fd.

## 3. What is the role of friction in calculating work?

Friction is a force that opposes motion, so when an object is moving against a surface with friction, the work done is affected. Friction can either increase or decrease the amount of work done, depending on the direction of motion and the type of friction present.

## 4. How does the coefficient of friction affect the calculation of work?

The coefficient of friction is a measure of the frictional force between two surfaces. It is a dimensionless number that can vary depending on the materials in contact and the surface conditions. The coefficient of friction affects the amount of work done by either increasing or decreasing the force needed to overcome friction.

## 5. What are some real-life applications of calculating work without friction?

Calculating work without friction is important in understanding the efficiency of machines, such as pulleys and gears. It is also used in analyzing the motion of objects in space, where there is no atmosphere to create friction. Additionally, calculating work without friction is essential in designing and optimizing transportation systems, such as trains and cars, to reduce energy consumption and increase efficiency.

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