10 minutes maximum! Can you do it in 5?

1+2: These questions are about friction:

  

1. The symbol µs in the IB data book refers to the quantity..

  • A. the force of friction.
  • B. the coefficient of static friction.
  • C. the efficiency of friction
  • D. the frictional constant

2. If µd is equal to 0.5, this means that the maximum force produced by friction on a moving object is half the size of ..

  • A. the weight of the object.
  • B. the driving force moving the object.
  • C. the normal force (reaction) of the surface on the object.
  • D. the air resistance on the object.

 

3-5. A book of mass 1.0 kg rests on a rough horizontal surface with µs= 0.4.

 

 book cartoon

3. What is the approximate value of the normal force (reaction) on the book?

  • A. 1.0 N
  • B. 0.4 N
  • C. 10 N
  • D. 4 N

4. What is the maximum frictional force preventing the book moving to the left or right if pushed?

  • A. 1.0 N
  • B. 0.4 N
  • C. 10 N
  • D. 4 N

5. The horizontal surface is raised at one end so that the book rests on a slope. It remains stationary. What happens to the sizes of the normal force (reaction) and the maximum force of static friction as the surface is lifted at one end?

 Normal force Maximum force of static friction
A
 decreases decreases
B
 decreases increases
C
 increases decreases
D
 increases increases

 

6. This large cruise liner has a very high mass. It also displaces a large volume of water.

When floating in the ocean, which of the following statements is true?

 cruise liner
  • A. The mass of water displaced is equal to the mass of the boat that is under the water
  • B. The weight of water displaced is equal to the weight of the boat that is under the water
  • C. The weight of water displaced is equal to the total weight of the boat
  • D. The volume of water displaced is equal to the total volume of the boat

 

7-10: A student is investigating how the radius r of an aluminium ball affects the terminal velocity when falling through oil. The ball is acted on by several forces including the weight of the ball W, a boyancy force Fb and a viscous force Fv.

 ball in oil, measuring cylinder

7. If the radius of the steel ball is doubled, what affect does this have on W and Fb?

 W Fb
A
 4 times larger doubles
B
 4 times larger 8 times larger
C
 8 times larger 4 times larger
D
 8 times larger 8 times larger

8. When falling through the oil at terminal velocity, which of these statments is true?

  • A. The forces are balanced, and W = Fv + Fb
  • B. The forces are balanced, and W = Fv - Fb
  • C. There is a net downward force of magnitude W - (Fv + Fb)
  • D. There is a net downward force of magnitude W - Fb + Fv

9. The ball eventually rests on the bottom of the cylinder. If the volume of the ball is V, and the density of the oil is ρoil then the normal force FN from the cylinder base acting on the ball is:

  • A. FN = g(m + ρoilV)
  • B. FN = (m + ρoilV)
  • C. FN = g(m - ρoilV)
  • D. FN = (m - ρoilV)

10. The ball is changed to a different material of the same radius but with 3 times the density.
How does this affect the terminal velocity?

  • A. Terminal velocity decreases
  • B. Terminal velocity stays the same
  • C. Terminal velocity increases
  • D. The ball floats and has no terminal velocity