Energy problem on toy cannon

[wachaif]

A toy cannon uses a spring tp project a 5.3 g soft rubber ball. The spring is originally compressed by 5 cm and has a force constant 8N/m .When the cannon is fired , the ball moves 15cm through the horizontal barrel of the cannon ,and there is a constant friction force of 0.032 N . between the barrel and the ball.At what point does the ball have maximum speed ? What is this maximum speed?

The Point the ball attain the Max speed is 4.6 cm after release
The Max Speed is 1.79m/s

Can anyone show me the step to obtain the answer ?THX

 

[Doc Al]

Here's the idea. At first, the force exerted by the spring is greater than the friction force that opposes the motion. So the ball accelerates until the spring force equals the friction force. That's the point that the ball has max speed. Find that point.

Then use conservation of energy to find the KE at that point.

 

[wachaif]

Thanks you .I got it