What happens when a ball is thrown vertically in the air?

[stephi]

Homework Statement

A ball is thrown vertically in the air, upward from the surface of the Earth. Which of the following quantities are zero when the ball reaches maximum height?
a)speed b)velocity c)acceleration

Homework Equations

The Attempt at a Solution

i answered just b, but i got it marked wrong so i am unsure. any thoughts?

 

[Doc Al]

What's the reasoning behind your answer?

 

[stephi]

because when the ball reached maximum height, the ball stops and then changes direction, so then it would have v=0 and the top. but would the speed be 0 as well?

 

[Doc Al]

You tell me. What's the relationship between speed and velocity?

 

[stephi]

velocity has to have direction while speed does not.

 

[Doc Al]

velocity has to have direction while speed does not.

Good. Speed is just the magnitude of the velocity. So how would you revise your first answer?

 

[stephi]

both speed and velocity will be zero?! :)

 

[Doc Al]

both speed and velocity will be zero?! :)

Of course.

 

[stephi]

thank you so much!
is there any chance you could also help me with a math problem that is giving me lots of trouble?

 

[Doc Al]

is there any chance you could also help me with a math problem that is giving me lots of trouble?

Did you post it?

 

[stephi]

yes but no replies yet,.