Question

Rosa studies the position-time graph of two race cars. A graph titled Position versus Time shows time in hours on the x axis, numbered 0 to 5, position in kilometers on the y axis, numbered 0 to 50. The graph has two straight lines, one from point (0, 20) up to (2.8, 50), the second line starts at the origin and goes to point (5, 20). Rosa concludes that truck X has a greater velocity than truck Y, and that truck Y had a head start. She also concluded that the graph shows both trucks moving at a constant velocity and that neither truck changes direction. Which statement best describes Rosa’s error?
A Both trucks change direction after they start moving.
B Truck X had a head start, not truck Y.
C Truck Y has a greater velocity than truck X.
D The trucks are not traveling at constant velocities.

Answer 1

Answer:

Answer is C

Explanation:

Just took the test and got it right

Answer 2

The truck represented by the first line has greater velocity.

Velocity of the trucks

The velocity of the trucks is determined from change in displacement per change in time.

v = dx/dt

From the first line at (0, 20) and (2.8, 50)

The velocity is calculated as follows;

v = (50 - 20)/(2.8 - 0)

v = 30/2.8

v = 10.71 km/h

From second line at (0,0) and (5, 20)

The velocity is calculated as follows;

v = (20 - 0) / (5 - 0)

v = 20/5

v = 4 km/h

Thus, the truck represented by the first line has greater velocity.

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