MCAT Work and Friction Problem

In summary, the question is asking which statement is true about the work done in a block sliding to a stop on a table top. Option D is the correct answer because it takes into account the changes in both kinetic and internal energies, while option A only considers the work done by friction in terms of force and distance. The concept of displacement versus distance is important in understanding why option A is incorrect.
  • #1
Taminem
2
0

Homework Statement



A block slides to a stop along a table top. Which of the following statements is true?

A. The work done by friction is equal to the force of friction times the distance that the block slid.
B. The work done on the block is equal to the force of friction times the distance that the block slid.
C. The work done on the table is equal to the force of friction times the distance that the block slid.
D. The work done on the block is equal to the sum of its changes in kinetic and internal energies.

Homework Equations


W = Ffr*d


The Attempt at a Solution


The answer given by the book is D but I do not understand why A is the incorrect answer. I thought if friction is doing work against the direction of motion of the block it would just equal exactly as what is stated - force of friction direction parallel to motion times the distance? As for D, wouldn't it be equivalent to A since whatever changes in potential and kinetic energy would entail and equivalent change in friction?

I'm really new to physics, so I'm missing very key concepts that I am not able to piece together. So thank you for your help and patience.
-Taminem
 
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  • #2
do you have any image of how the block was sliding ?

work done by friction depend on distance no displacement --- maybe that's why A is wrong coz problem may be referring to displacement
 
  • #3
Hi cupid.callin,
Thanks for the reply. Turns out there is no image of how the block was sliding. However, your comment made me reread the equation for work and realize why D is the answer and not A. Since, d in the work equation is displacement and not distance, like the phenomenon of rubbing two hands together, no displacement is done since the positions of the hands in the initial state and final state are the same, but work is still done in the form of increasing the internal energy/temperature of the hands at the expense of kinetic mechanical energy. Thus, work done by frictional forces is not just Ffr * d but the change in Eint and mechanical energy.

Thanks for your reply! It was really useful.
 

1. What is the MCAT Work and Friction Problem?

The MCAT Work and Friction Problem is a type of physics problem commonly found on the Medical College Admission Test (MCAT). It involves calculating the amount of work done against frictional forces in a given situation.

2. How is work defined in physics?

In physics, work is defined as the product of force and displacement, or the amount of energy transferred to or from an object. It is typically measured in units of joules (J).

3. What is friction and how does it affect work?

Friction is a force that opposes the motion of an object. It is caused by the roughness of surfaces in contact with each other. In the context of work, friction can reduce the amount of work done by a force, as some of the energy is lost to overcoming frictional forces.

4. Can you provide an example of an MCAT Work and Friction Problem?

Sure, an example problem might involve a block being pushed along a rough surface with a force of 10 N over a distance of 5 meters. The coefficient of friction between the block and the surface is 0.4. The question might ask for the amount of work done against frictional forces in this situation.

5. How can I improve my problem-solving skills for MCAT Work and Friction Problems?

To improve your problem-solving skills for MCAT Work and Friction Problems, it is important to practice solving a variety of problems and understanding the underlying concepts. It can also be helpful to break down the problem into smaller, more manageable steps and to use visual aids such as diagrams or graphs to better understand the situation.

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