1. Homework on forces that involve friction

2. Question 1
Derek is playing cards with his friends, and it is his turn to deal.
A card has a mass of 2.3 g, and it slides 0.35 m along the table before it stops.
If the coefficient of kinetic friction between the card and the table is 0.24, what was the initial speed of the card as it left Derek’s hand?

3. Q2
While riding in a helicopter, you drop two ping-pong balls, one filled with air and the other water. Both experience air resistance as they fall. Which ball reaches terminal velocity first? Do they both hit the ground at the same time? Explain your answers

4. Q3
A 200 kg crate is pushed horizontally with a force of 700 N. If the coefficient of friction is 0.2, calculate the acceleration of the crate

5. Q4
In what direction does the force of air resistance act?

6. Q5
Draw a free body diagram of a box sliding down a ramp showing all forces on box. Assume that there is friction, and that the ramp is at a 45 degree angle to the ground.

7. Q6
A 1546 kg car skids to a stop on a rough road. If the coefficient of friction is 0.56 and the initial speed was 39 m/s, determine the following: a) A free body diagram and the amount of frictional force on the car b) The net force on the car as it slows down c) The overall displacement of the car and the amount of time required to stop.

8. Q7
Is there friction between 2 objects that are not moving? Explain

9. Q8 What features of and object in a location determine the amount of friction that exists?

10. Q9 If there was no friction in the world….
Would my shirt immediately fall off?
Would I not be able to see anything?
Would it be impossible to take a step?
Would magnets stay in the same place on a refrigerator?
Explain your responses

11. Question 10
Explain why an object falling out of an airplane does not continue to accelerate forever.

12. Question #11
During a fuel economy test of a sports car, the car achieved more miles per gallon of gasoline when its convertible top was up. Explain, in terms of forces, how the top being up or down affects the car’s fuel economy