Potential energy of ball thrown upwards

[sp3sp2sp]

Homework Statement

A 1.00 kg ball is thrown directly upward with an initial speed of 16.0 m/s.
A graph of the ball's gravitational potential energy vs. height, Ug(h), for an arbitrary initial velocity is given in Part A. The zero point of gravitational potential energy is located at the height at which the ball leaves the thrower's hand.

PART A: Draw a line on the graph representing the total energy E of the ball.
For this problem, take g=10.0m/s2 as the acceleration due to gravity.

(I did this part correctly and it is the horixontal line on the graph)

PART B: Draw a new gravitational potential energy vs. height graph to represent the gravitational potential energy if the ball had a mass of 2.00 kg. The graph for a 1.00-kg ball with an arbitrary initial velocity is provided again as a reference.

Take g=10.0m/s2 as the acceleration due to gravity

2. Homework Equations
(1/2)mv^2 = -mgh

The Attempt at a Solution

the horizontal line on the attached graph is the answer to part A, which asked "Draw a line on the graph representing the total energy E of the ball."

For part B, I thought that because mass cancels in the equation that total but I then realized it asks about total gravitational PE, (=mgh) not total energy . So I am now confused how to represent that on the graph?

thanks for any help

 

[kuruman]

There are two lines on the graph. You identified the horizontal line as the total energy in part A and that is correct. What do you think the second line represents? Hint: Read the statement of the problem.

 

[sp3sp2sp]

thanks for reply. according to statement it is grav PE vs height. But what confuses me is how to represent the grav PE. I mean it depends on what h and m are, so is the question asking for another PE vs height (sloped) line?

 

[kuruman]

... so is the question asking for another PE vs height (sloped) line?

Yes, you are shown the graph of PE vs. h when the mass is 1.0 kg and you are asked to draw PE vs. h when the mass is 2.0 kg. What do you think the second plot should look like?

 

[sp3sp2sp]

mass doubled so same line but double the slope? (because mg = slope?)

 

[kuruman]

mass doubled so same line but double the slope? (because mg = slope?)

Correct.