Potential Gravity Energy Question

[MacMilla]

Homework Statement

An athlete throws a basket ball in a net. He releases the ball at a height of 0.50m with a velocity of 9.0m/s. Calculate the velocity of the ball once it "slides" down the net. The net is at a height of 3.0m and at a distance of 5.0m from the athlete.

I attached the sketch of the problem.

Homework Equations

ET1 = ET2
Eg1 + Ec1 = Eg2 + Eg2

The Attempt at a Solution

mgh1 + mv1^2/2 = mgh2 + mv2^2/2
9.8 x 0.5 + 0.5x9^2 = 9.8 x 3 + 1/2V2^2
This is obviosly too simple, and doesn't give the right anwer.
So what should i do??

 

[MacMilla]

anyone?

 

[MacMilla]

any help?

 

[Doc Al]

Have you presented the problem exactly as given? Assuming the data is correct, then your method should work fine.

 

[Doc Al]

He releases the ball at a height of 0.50m with a velocity of 9.0m/s.

Are you sure it doesn't say something like "at a height of 0.50m below the net"? That would match the diagram more closely.

 

[MacMilla]

the sketch is not to scale
but the ball is thrown at a height of 0.5m, it doesn't make much sense, but that's what the question says.

 

[Doc Al]

the sketch is not to scale
but the ball is thrown at a height of 0.5m, it doesn't make much sense, but that's what the question says.

In that case, your approach is correct. Assuming that "once it "slides" down the net" means when it passes through the net.

 

[MacMilla]

yes, but I haven't taken into consideration the 5m distance seperating the player from the net, therefore, what I have done is incorrect.

 

[Doc Al]

yes, but I haven't taken into consideration the 5m distance seperating the player from the net, therefore, what I have done is incorrect.

Assuming the problem is stated correctly, that information is irrelevant.

 

[MacMilla]

well, in the book, the correct answer is 8.4m/s,
i got 5.65m/s

 

[Doc Al]

What book are you using?

 

[MacMilla]

Its a French Book, I go to a French High School
Its called Physique 12