Question

question 4 (3 points)
(01.09 mc)
a speed versus time graph is shown:
speed vs. time graph: x - axis labeled time (s), y - axis labeled speed (cm/s). from 0 to 4 seconds, the speed increases linearly; from 4 to 8 seconds, the speed is constant (horizontal line).
which statement accurately describes the motion of the object in the graph above?

○ a it is moving from 0 s to 4 s at a constant speed of 2 cm/s.
○ b it is at rest for 4 seconds from 4 s to 8 s and then speeds up.
○ c it is moving from 4 s to 8 s at constant speed of 4 cm/s.
○ d it is speeding up from 0 s to 4 s then it is at rest.

Explanation:

• Option a: From 0 s to 4 s, the speed - time graph is a straight line with a positive slope, which means the object is accelerating (speeding up), not moving at a constant speed. So option a is incorrect.
• Option b: From 4 s to 8 s, the speed - time graph is a horizontal line, which means the object is moving at a constant speed, not at rest. So option b is incorrect.
• Option c: From 4 s to 8 s, the speed - time graph is a horizontal line at \(v = 4\space cm/s\), which means the object is moving at a constant speed of \(4\space cm/s\) during this time interval. This statement is correct.
• Option d: From 4 s to 8 s, the object is moving at a constant speed, not at rest. So option d is incorrect.

Answer:

c. It is moving from 4 s to 8 s at constant speed of 4 cm/s.