Physics Help: Interpreting Position-versus-Time graphs?
"Could someone help me interpret a position-versus-time graph? I need to find the object's speeds, v1, v2, and v3, at three different times: t1 = 2.0 s, t2 = 4.0 s, and t3 = 13 s. The answers should be in meters per second, rounded to two significant figures, and separated by commas.
Unfortunately, I can’t share the graph directly since it’s part of a homework problem on MasteringPhysics.com, which requires a password to access. However, I’ve triple-checked the data, and the object's positions are as follows: 4 m at t1, 7 m at t2, and 9 m at t3.
To calculate the velocity, isn’t it just the change in position divided by the change in time? Using that approach, I calculated the velocities as 2.0 m/s, 1.75 m/s, and 0.69 m/s, but Mastering Physics says my answers are incorrect.
Where might I be going wrong? Any guidance would be greatly appreciated! Thank you!"
5 Answers
You need to use the formula Velocity = Distance / Time.
Since it started from 0 you can say your change in position for t1 is 4 meters. So it’s 4 meters / 2 seconds for t1. You get 2 m/s.
For t2 you go from t1 to t2 a total of 3 meters. So it’s 3 meters / 2 seconds. So it’s 1.5 m/s.
For t3 you go from t2 to t3 a total of 2 meters. It takes 9 seconds. So it’s 2 meters / 9 seconds which is .22 m/s (approximately)
See if that works. The question should say if it wants between certain time intervals or the average velocity.
The velocity is the slope of a displacement vs time graph.
At t = 0 s, x = 0 m, at t = 2 s, x = 4 m
If the graph, for the 1st period of time, is a straight line, slope = ∆x/∆t = 4/2 = 2
Average velocity during this time is 2 m/s.
During the next 2 seconds, the object moves from 4 m to 7 m.
∆x = 3 m, ∆t = 2 s,
If the graph, for the 2nd period of time, is a straight line, slope = 3/2 = 1.5 m/s
Average velocity = 1.5 m/s
During the next 9 seconds, the object moves from 7 m to 9 m
If the graph for the 3rd period of time is a straight line, slope = 2/9 = 0.222 m/s
Average velocity = 0.222 m/s
Feb 21, 2025
Find Slope for each one:
t1= 7/3 = 2.3m/s
t2= 0 =0m/s
t3= 3/5 =0.60m/s
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