How Long Did the Power Delivery to the Ball Last?

[pinnacleprouk]

Thanks in advance, I just want to double check!

Homework Statement

A 5 kg ball is tossed into the air with an initial velocity of 6m/s.
a) What is the kinetic energy of the ball?
b) If the power delivered to the ball was 100watts, over what time interval did
the power delivery occur?

Homework Equations

K.E = 1/2 mV*2

P = E/t

The Attempt at a Solution

a)... using K.E = 1/2 mV*2 answer is 90J

b)... using P = E/t answer is 0.9s

 

[Doc Al]

Looks good!

 

[stanton]

But I am a bit confuesd, is initial velocity is equal to velocity in the equation?In other words, can we plug the value of initial v in v in the equation? Shouldn't we try to get velocity?

 

[Doc Al]

But I am a bit confuesd, is initial velocity is equal to velocity in the equation?In other words, can we plug the value of initial v in v in the equation? Shouldn't we try to get velocity?

The velocity is given. It's the velocity of the ball immediately after leaving the hand.

 

[pinnacleprouk]

Thanks for the replies

 

[stanton]

Now I get it. :) Thanks! I am having difficulty with treating problems related to kinetic energy and power.