# PHYSICS 151

##### University of Hawaii, Manoa Dept. of Physics & Astronomy

Instructor: Michael Nassir
Office: Watanabe Hall, Rm. 426, (808) 956-2922
E-mail: nassir @ hawaii.edu

## ANSWERS to MIDTERM #2 from SPRING 2004

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.)