MC	Physics	Standard: 01
Objective: 03. Relate the motion of objects to a frame of reference.
ILO:

Jane is driving north at 20 m/s. Betty is driving south at 15 m/s. How would the observed motion of each driver compare, relative to each other?

a. Each driver observes the other at 35 m/s, relative to herself.

b. Each driver observes the other at 5 m/s, relative to herself.

c. Jane sees Betty driving at 20 m/s; Betty sees Jane driving at 15 m/s.

d. Jane sees Betty driving at 15 m/s; Betty sees Jane driving at 20 m/s.

Correct Answer: a

MC	Physics	Standard: 01
Objective: 03. Relate the motion of objects to a frame of reference.
ILO:

An airplane drops a rescue pack to a group of stranded hikers.

1. What type of path do people in the plane observe that the packet follows?

a. The packet falls straight down vertically from the plane.

b. The packet takes a straight diagonally downward path.

c. The packet flies horizontally with the plane for a time and then falls diagonally downward.

d. The packet falls downward in a parabola-shaped path.

2. What type of path do the hikers observe that the packet follows?

a. The packet falls straight down vertically from the plane.

b. The packet takes a straight diagonally downward path.

c. The packet flies horizontally with the plane for a time and then falls diagonally downward.

d. The packet falls downward in a parabola-shaped path.

Correct Answers:

1. a

2. d

E	Physics	Standard: 01
Objective: 03. Relate the motion of objects to a frame of reference.
ILO:

Once there were three fireflies. The names of the fireflies were Albert, Barney, and Charles. One day they decided to take a ride on a bicycle. Albert located himself on the front wheel of the bicycle very near the outside of the tire, but not in a position to be smashed as the wheel rotated. Barney located himself on the frame of the bicycle in a position where Albert could see him. Charles located himself on the axle of the front wheel. Now this was a very thin axle and Charles was essentially at the center of the front wheel. Assume that it is a dark night and the only light to be seen is that generated by the three fireflies.

Answer two of the following questions.

1. Describe the relative motion of Barney and Charles as seen by Albert. Use diagrams as necessary.

2. Describe the relative motion of Albert and Charles as seen by Barney. Use diagrams as necessary.

3. Describe the relative motions of Albert and Barney as seen by Charles. Use diagrams as necessary.

4. Describe the motions of Albert, Barney and Charles as seen by an observer standing to the side of the road as the bicycle moves by.

Correct Answers:

Answers will vary. Allow two points for each description of motion if it includes correct diagrams.

1. Albert would see Charles as fixed in position or not moving. Albert would see Barney as moving in some fixed circle of motion centered at Charles and moving around both Albert and Charles. There would be times that Barney would be much closer than at other times.

2. Barney would see Charles as fixed in position, but kind of spinning on his axis. Barney would see Albert as moving in a circle about Charles with the circle passing between Charles and Barney.

3. Charles would see Albert as fixed in position or not moving. Charles would see Barney as moving in a circular orbit about himself. He would appear to come up and go down on a regular basis.

4. An observer would see Albert moving in a cycloid type motion. An observer would see Barney moving in a straight line. An observer would see Charles moving in a straight line (considering the axle very, very small) or a very small cycloid if the axle had significant diameter.