Dept. of Physics & Astronomy

Office: Watanabe Hall, Rm. 426, (808) 956-2922

E-mail: nassir @ hawaii.edu

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PHYS 151 Exam & Answers page*

**Part A**

**1a.** ellipse

**1b.** "fastest" at point of closest approach to
the Sun; "slowest" at point of farthest distance from
the Sun

**1c.** Sedna

**2a.** B

**2b.** B (gravitational force between any two masses is always
attractive)

**2c.** B

**3a.** E

**3b.** A

**4a.** F

**4b.** C (must be a force that points toward the axis of rotation)

**5a.** 30,000 J (since speed of car at point B is virtually
zero, so KE at point B is virtually zero)

**5b.** 30,000 J

**5c.** D

**5d.** C

**5e.** C (if PE at point A is 18,000, then KE at point A is
12,000 J, and KE = (1/2)*m v*^2)

**6.** C

**Part B**

**1a.** 220 km/s or 2.2 x 10^2 km/s

**1b.** 1.83 x 10^41 kg

**1c.** 92 billion stars

**2a.** Weight (straight down = toward center of Earth);
Normal force (to upper left, perpendicular to ramp); Tension (to
upper right, parallel to ramp)

**2b.** 5460 N or 5.46 x 10^3 N

**2c.** C

**2d.** 13.3 m/s (Note: If using conservation of energy, the
crate starts from an initial *vertical* height of 9.03 m.)