Graphical analysis, vx, ax, and xf problems

[mark9159]

1.) A car travels at 15 m/s for 10s. It then speeds up with a constant acceleration of 2.00 m/s^2 for 15s. At the end of this time, what is its velocity?

My answer: Vxf= 45 m/s

2.) An object is moving in a straight line with constant acceleration. Initially it is traveling at 16 m/s. Three seconds later it is traveling at 10 m/s. How far does it move during this time?

My answer: 39m

3.) A ball is thrown downward from the top of a building with an initial speed of 25 m/s. It strikes the ground after 2.0s. How high is the building?

My answer: 30m

4.) I can't draw a graph on here, so I'll describe it to the best of my abilities. It is a velocity versus(m/s) vs. time (s) graph.

The graph starts at the origin. At 2.0s, velocity increases 20 m/s. From 2.0 to 4.0 seconds, velocity is constant at 20m/s. From 4.0 to 6.0s, velocity is decreasing by 20 m/s. At 6.0 to 8.0s, velocity is decreasing another 20 m/s.

question: What is the displacement from 0 to 8.0s?

My answer: Honestly, I didn't know how to approach this one. All i did was I added up and subtracted...and got 20m.

5.) Which student used the least precise scale?
A. 49.06
B. 49
C. 50
D. 49.2

 

[SGT]

1.) A car travels at 15 m/s for 10s. It then speeds up with a constant acceleration of 2.00 m/s^2 for 15s. At the end of this time, what is its velocity?

My answer: Vxf= 45 m/s

2.) An object is moving in a straight line with constant acceleration. Initially it is traveling at 16 m/s. Three seconds later it is traveling at 10 m/s. How far does it move during this time?

My answer: 39m

3.) A ball is thrown downward from the top of a building with an initial speed of 25 m/s. It strikes the ground after 2.0s. How high is the building?

My answer: 30m

4.) I can't draw a graph on here, so I'll describe it to the best of my abilities. It is a velocity versus(m/s) vs. time (s) graph.

The graph starts at the origin. At 2.0s, velocity increases 20 m/s. From 2.0 to 4.0 seconds, velocity is constant at 20m/s. From 4.0 to 6.0s, velocity is decreasing by 20 m/s. At 6.0 to 8.0s, velocity is decreasing another 20 m/s.

question: What is the displacement from 0 to 8.0s?

My answer: Honestly, I didn't know how to approach this one. All i did was I added up and subtracted...and got 20m.

5.) Which student used the least precise scale?
A. 49.06
B. 49
C. 50
D. 49.2

For question 4. Since displacement is the integral of velocity, you should calculate the area under the velocity curve, from 0 to 8 secods.

 

[quicknote]

My answer: B. 49

Explanation: The least precise scale is the one with the fewest number of digits after the decimal point. In this case, option B has no digits after the decimal point, making it the least precise.