Bouncing Ball Problem, velocity vs. time

[kingneb]

This is my first college physics class and I am feeling a little challenged, since it is the start and all. I took physics in high school and am a bit rusty. I appreciate any help.

Homework Statement

The vertical component of the velocity of a bouncing ball is shown in the graph below (graph is very large). The positive Y direction is vertically up. The ball deforms slightly when it is in contact with the ground.

[PLAIN]http://img180.imageshack.us/img180/494/graphz.png

They want for part a: Identify the instances in time where the ball is at maximum height.

Homework Equations

None really for part a. Part b asks you to calculate the average velocity while the ball is in the air. Part c, when it is on the ground. Part d asks for the maximum height above the floor using the area under the graph. So for parts b and c I guess you have to use a = v / t. I will probably need some help with these. I will continue the thread when I finish part a.

The Attempt at a Solution

I am kind of mixed up on where to start for part a. I do know the vector direction is negative where the line slopes are negative, and positive respectively. At this point I am assuming that the ball is falling when the function is below the x-axis and rising when it is above the x axis.

 

[Daft]

You're correct in that the ball is falling when the function is below the x axis

Think about what the gradient of a line at any point on the graph represents, and how this is affecting the velocity.

When the ball is at maximum height, what would the velocity at that point be?

 

[kingneb]

So, maximum height is denoted by when the the function crosses zero?

 

[Daft]

That's only half correct, its not every time the function crosses zero

 

[kingneb]

So does the ball hitting the floor happen at 1.125 seconds, 3.875 seconds?

Max Height 0 seconds, 2.25 seconds, and 5 seconds?

 

[Daft]

Correct

 

[PhanthomJay]

So does the ball hitting the floor happen at 1.125 seconds, 3.875 seconds?

The ball has no velocity at t=1.125 and t= 3.375 seconds (you misread the graph on that last figure), but the ball hits the floor at 9m/s, when t=? and ?

 

[Daft]

Ahh yes, I was wrong with respect to that, my apologies

I was focusing too much on maximum height, and missed that error