Question

(15 POINTS)The graph below shows Lisa's distance from her home (y), in miles, after a certain amount of time (x), in minutes:

Four students described Lisa's motion, as shown in the table below:




Student Description
Greg She drives at a variable speed for 2 minutes, then stops at a crossing for 2 minutes, and finally drives at a constant speed for the next 4 minutes.
Sam She drives at a variable speed for 2 minutes, then stops at a crossing for 4 minutes, and finally drives at a constant speed for the next 8 minutes.
Jane She drives at a variable speed for 2 minutes, then drives at a constant speed for the next 2 minutes, and finally drives at a variable speed for the next 4 minutes.
Pam She drives at a variable speed for 2 minutes, then drives at a constant speed for 4 minutes, and finally drives at a variable speed for the next 8 minutes.


Which student most accurately described Lisa's motion?
Greg
Sam
Jane
Pam

Answer 1

Greg is the most correct:

She drives at a variable speed for 2 minutes, then stops at a crossing for 2 minutes, and finally drives at a constant speed for the next 4 minutes.

Answer 2

Option A. Greg is the answer.

Explanation:

From the graph given, we have to analyze Lisa's motion at time t = 2 min , t = 2 to 4 min. and t = 4 to 8 min.

1). At time t = 2 min.

Graph shows that Lisa drives at different speeds from t=0 to t=2 min.

2). From t = 2 to t = 4 min.

Since Lisa has not covered any distance during this period, means she stopped at a crossing.

3). From t = 4 to t = 8 min.

Lisa covered distance from 2 to 6 miles in 4 min. with a constant speed.

We can calculate at every minute speed of Lisa was constant and equal to 1 mile per min.

Now it is clear that Greg described Lisa's motion most accurately.