Friction Poster Activity

Introduction

THIS IS A SUMMATIVE ASSESSMENT TO ASSESS YOUR UNDERSTANDING OF THE PHENOMENON OF FRICTION. NOTES  ALLOWED. FEEL FREE TO USE VIDEOS AND ARTICLES TO DEEPEN YOUR UNDERSTANDING AND HELP YOU WITH THE SOLUTIONS.

INSTRUCTIONS:

  • Activity: Each one of you will choose 1 question from Section A and 1 question from Section B and answer them on the provided poster paper

  • As a group, you must answer 4 different questions from Section A and 4 different questions from Section B.

  • Each member will use a different color of marker. Please work out the solution in your notebook first, before writing on the poster.

  • Your answer must have the following:

    • All Laws and/or equations used.

    • List of givens, list of unknowns, equation, substitution with units, and solution.

    • Write the correct units in each step of the solution and the final answer.

  • 3- 4 members per group.

  • Mastery-based grading which means you will be evaluated based on your work.

  • Due by the end of the class period. Penalty for late submission: -1 pt/ day

Task

 

Section A (each member of the group selects one from this section, no repetitions)

Take g = 9.8 ms–2

Q1) A parcel of mass 2 kg lies at rest on a rough horizontal surface, as shown.

  1. i  Draw a force diagram showing the forces acting on the parcel.

  2. ii  Calculate the normal contact force, R.

 

Q2) The parcel is now pushed with a horizontal force P, as shown, so that it is just on the point of sliding.

  1. i  Draw a force diagram showing the forces now acting on the parcel.

  2. ii  If the coefficient of friction is 0.5, find the value of P when the parcel is on

the point of sliding.

Q3) A dustbin of mass 12 kg standing on horizontal ground is pushed by a horizontal force of 40 N.

If the coefficient of friction is 0.4, will the dustbin move?

Q4) A conveyor belt is used to carry cans from one part of a factory to another. Each can has mass 350 grams.

If μ = 3/4 and each can is just on the point of sliding, find the frictional force acting on each can.

Q5)  A sledge has mass 15 kg. A horizontal pull of 25 N will just move the sledge when it is on a horizontal surface of compacted snow.

a Draw a diagram showing the forces acting on the sledge, modelled as a particle, when it is just on the point of sliding on this horizontal surface.

b Find a value for μ, , the coefficient of friction between the surfaces.

Q6) One end of a light inextensible string is attached to a tool box of mass 2.5 kg which is lying on a horizontal table.

The string passes over a smooth pulley and is tied at the other end to a bag of mass 1.4 kg.

  1. a  Draw a diagram showing the forces acting on the tool box.

  2. b  If the tool box is just on the point of sliding, find a value for μ,the coefficient of friction.

 

Section B (each member of the group select one from this section, no repetitions

Combining the friction model with Newton’s Second Law and the constant acceleration equations

In the following problems you will need to combine the friction model with Newton’s Second Law and the constant acceleration equations.

Q7)  A car of mass 1 tonne is travelling along a straight horizontal road at 15 ms–1 when it brakes sharply then skids. Friction brings the car to rest.

If the coefficient of friction between the tyres and road is 0.75, calculate:

  1. a  the deceleration

  2. b  the time taken for the car to come to rest.

Q8) A cup of coffee of mass 250 grams sits on a table in a train carriage. The train accelerates at 1.2 ms–2 out of a station.

  1. a  Draw the forces acting on the cup of coffee.

  2. b  If the cup does not slip, find the value of the friction force acting on the

cup of coffee.

c If the cup is just about to slip, find the coefficient of friction between the cup and the surface of the table.

Q9) A woman is trying to push a load of mass 50 kg across a floor. The woman exerts a force of 70 N.

a Modelling the floor as smooth and the load as a particle, calculate the acceleration of the load.

b Assuming that a constant resistive force of 56 N is acting, calculate:

  1. i  the acceleration of the load

  2. ii  the coefficient of friction, , between the load and the ground, assuming

the resistive force is due only to friction.

Q10) A trunk of mass 30 kg is standing on a horizontal floor.

The coefficient of friction, μ, between the trunk and floor is 0.3.

  1. a  Find the maximum value the friction can attain.

  2. b  Find the force that is necessary:

  1. i  to keep the trunk sliding over the floor with constant speed

  2. ii  to cause the trunk to slide over the floor with acceleration 0.2 ms–2.

 

Process

Reference

 

https://www.youtube.com/watch?v=J9BWNiOSGlc

Static vs kinetic friction overview

https://www.youtube.com/watch?v=ZA_D4O6l1lo

Sample problems

 

https://www.youtube.com/watch?v=n1mmqM0qp6A

Graphical representation of Friction force vs Applied force AND Friction force vs Normal reaction

Reading:

https://openstax.org/books/university-physics-volume-1/pages/6-2-friction

Evaluation

Total points possible -20

  • Hard deadline: 11/08/23

  • Late submission penalty: -1pt/ Day

Rubric

 

Exceeds expectation- 4

Meets expectations- 3

Almost there-2

Not there yet-1

Laws and/or equations

All laws and/or equations are correctly selected, and written in strategic places, which makes the solution easier to understand. All the variables used in it are described.

All laws and/or equations are correctly selected, and written, and the variables used in it are described.  But not placed strategically and does not enhance comprehension.

All laws and/or equations are correctly selected, and written, but not strategically placed and variables are not described.

Laws/equations are either completely absent or incorrectly selected.

Correctness

All sub-parts and the final answer is correct.

All sub-parts are correct but the final answer has an error.

One or more sub-parts and the final answer is wrong.

Did not understand the question.

Diagrams

Diagrams are present in all required places and labeled accurately.

Diagrams are present in some places and labeled accurately.

Diagrams missing in most parts and not labeled.

No diagrams

GUESS

Give, unknown, equation, substitution, and solution all present with correct units at every step, as well as the final answer.

One is missing from-Given, unknown, equation, substitution, or solution. Most of the steps have units and the final answer has units.

Two are missing from Given, Unknown, Equation, Substitution, or Solution. Units missing from the working steps but the final answer has unit.

No units anywhere

Visual appeal

Visually appealing, which makes the final product very interesting to look at and easy to understand. Shows the best effort.

Visually appealing, which makes the final product easy to understand. Shows a good amount of effort.

No visual appeal. Completed with bare minimum effort

No visual appeal. Shows zero effort or is incomplete.