Practice Test for Midterm 3 (Short Answer) s1

Practice test for Midterm 3 (short answer) (Chapter 10, 11, 12, 13, 14)

11. (Chapter 10) A disc, a sphere and a ring start rolling down an incline at the same time. They all have the same mass and diameter. In what order will they reach the bottom of the incline. a. All the same b. Disc, sphere, ring c. Disc, ring, sphere d. Sphere, ring, disc e. None of the above. My order is______

12. A cart of mass 1kg moving at 2 m/s along the positive x-axis rear-ends (collides) with a cart of mass 3 kg moving along the positive x-axis with 1 m/s. The cars stick together after the collision. Which statements are true and what is the velocity of the carts after the collision? a. The collision is elastic. b. The collision is inelastic. c. Momentum and kinetic energy are conserved in this collision. d. The velocity of the carts after the collision is______

13. Can the center of mass of an object lie outside the contiguous part of the object? If so, draw an object for which that is true. a. No b. Yes (Draw an example).

14. Which of the following quantities are conserved in an inelastic collision? a. Kinetic energy b. Momentum c. Velocity d. Force e. Acceleration 15. (Chapter 10) A uniform sphere of radius R and mass M rotates freely about a horizontal axis that is tangent to an equatorial plane of the sphere, as shown below. The moment of inertia of the sphere about this axis is

2 a. MR 2 . 5 2 b. MR 2 . 3 5 c. MR 2 . 7 7 d. MR 2 . 5 3 e. MR 2 . 2

16. (Chapter 10) The angular speed of the minute hand of a clock, in rad/s, is 1 a.  . 1800 1 b.  . 60 1 c.  . 30 d. . e. 120.

Chapter 11

25. The object shown below has mass m and velocity v. The direction of its angular momentum vector with respect to an axis perpendicular to the page through point O is

a. downwards. b. to the right. c. into the page. d. up out of the page. e. counterclockwise. 28. Five identical cylinders are each acted on by forces of equal magnitude. Which force exerts the biggest torque?

31. The diagram below shows five 20-kg rods of the same 2.0-m length free to rotate about axes through the rods, as indicated. Which rod experiences the greatest gravitational torque?

Chapter 12

15. The diagrams below show forces applied to a wheel that weighs 20 N. The symbol W stands for the weight. In which diagram(s) is the wheel in equilibrium?

a. A b. B c. C d. D e. A and C Chapter 13 Graviation

1. A planet moves around the sun on an elliptical path. a) Draw an ellipse and indicated at which point of the ellipse the sun could be located. b) Indicate in the same drawing at which point of the ellipse the planet is moving the fastest/slowest.

2. Calculate the gravitational acceleration on the moon given G, the radius of the moon and the mass of the moon (front of book).

4. Uranus is further from the sun than earth. Is its orbital period greater, equal or less than a year?

Chapter 14 Fluid Mechanics

1. If the top of your head has a surface area of about 100 cm2, what is the weight of the air above your head? 2. Will you float higher in the ocean or in a lake? 3. A lead cube and an iron cube of equal volume are submerged in water. Which one experiences the higher buoyant force? 4. Does a normal coke float or sink in water? How about a diet coke? 5. An approximately weightless aluminum can (volume 1 l) is filled with water. A Newton meter measures its weight in air and in water. What are the approximate values? 6. An ice cube floats on the surface of a glass of water. What happens to the water level as the ice cube melts (rise, fall, same)? 7. Why does a (slowly emerging) stream of water get thinner as it drops down? (Use an equation to explain). 8. A drop of water flows down a river (10 m deep, 10 m wide) at a speed of 1 m/s. It enters a lake that is 100 m deep, 1 km wide and 3 km long. How long will it take the drop of water to make it through the lake? (You may assume rectangular cross sections). Answers:

Chapter 10:

11e 12b, d 1.25m/s 13b 14b 15d 16a

Chapter 11: 25. c 28. a 31. e

Chapter 12: 15. c

Chapter 13: 1a. Sun is in one of the focal points. 1b. Look at Kepler’s 2. law 2. g ~ 1.6 m/s2 3. Use Kepler’s 3. law

Chapter 14: 1. Use air pressure and definition of pressure 2. In the ocean (sea water has higher density) 3. Buoyant force is the same (equal to weight of displaced volume) 4. remember class room demo 5. In air: 9.8 N; in water ~ 0N 6. level will remain the same 7. look at continuity equation 8. use continuity equation: 3x106 s = 34.7 days

Chapter 15: 1. A: larger period, smaller amplitude, smaller frequency, smaller ang. Frequency. 2. negative position, positive velocity (look at slope) 3. T for mass on spring depends on m and k. 4. ratio = (3/4)1/2