Target: How do I calculate friction and weight?
Warm-up:
A box has a weight of 30 N. It is at rest on the table. What is the magnitude of the Normal force on the
box?
2nd piece of the warm-up
Think for a second about the 2nd six weeks. Come up with 2 things that you could do better and 2
changes you would like for this six weeks.
Schedule:
1.
2.
3.
4.
5.
6.
Warm-up/ Check Reading
How to calculate weight given mass?
What is static and kinetic friction (what does the coefficient mean)?
Calculating friction based on Normal Force
Decomposing vector reviews
Reflection
Calculating weight given mass.
What is the weight of a cat with a mass of 15 kg?
What is your weight?
What is the weight of a dog with a mass of 40 lbs?
What is the method to find the weight of an object?
Static and Kinetic Friction (Chair Activity)
1. What affected both the static and the kinetic friction?
2. What was the difference between the static and the kinetic friction that you felt?
Using the table and your experience from the chair activity
Material
Steel on Steel
Aluminum on steel
Rubber on dry concrete
Rubber on wet concrete
Wood on Wood
Glass on Glass
Ice on Ice
Static coefficient
0.74
0.61
1.0
0.4
0.9
0.1
1. What is a general trend between static and kinetic friction?
2. Figure out a trend that exists in the data above?
3. What does the table actually tell us?
Kinetic coefficient
0.57
0.47
0.8
0.5
0.2
0.4
0.03
Level 1 Questions: Calculating Friction
Material
Steel on Steel
Aluminum on steel
Rubber on dry concrete
Rubber on wet concrete
Wood on Wood
Glass on Glass
Static coefficient
0.74
0.61
1.0
0.4
0.9
Kinetic coefficient
0.57
0.47
0.8
0.5
0.2
0.4
1. A steel box is placed on a steel table. If the steel box has a mass of 30 kg what is the minimum
force needed to get the box moving along the table?
2. An aluminum box is being pushed along a steel table at a constant speed. If the box has a mass
of 15 kg.
a. What is the force of friction on the box
b. What is the force being applied to the box
3. A piece of wood is being pushed across a level surface that is also made of wood with a force of
10 N. What is the mass of the wood if the wood is moving at a constant velocity?
Reflection:
Write at least 3 sentences detailing what you learned today. Concentrate on what you think you may
need more help on.
A box is at rest on an incline that is at an angle of 30 degrees. Find the magnitudes of all forces
acting on the box assuming the box has a mass of 3 kg.