How Fast Does a Ball Move When Pushed by Compressed Air?

[brunettegurl]

final velocity of a ball pushed by compressed air..pls. help!

Homework Statement

Compressed air is used to fire a 1.72 kg ball vertically upward from a 1.50 m long
tube. The air exerts a upward force of 28.7 N on the ball as long as it is in the tube.
With what velocity does the ball leave the top of the tube?

Homework Equations

F=ma
V₁² = v₀²+2ad

The Attempt at a Solution

so i used the given mass and force to get an acceleration. then using the acceleration i plugged it into the second equation assuming vinitial to be zero and my asnwer is coming out wrong can someone point me in the right direction thanks

 

[rock.freak667]

Resultant force= Upward force-downward force

what's the downward force in this case?

 

[brunettegurl]

wld the downward force be the friction..but there is no mention of any friction in the question

 

[rock.freak667]

wld the downward force be the friction..but there is no mention of any friction in the question

if you throw a ball upwards, it does not continue to go upwards, what makes it fall back to earth? (it has a mass m and is under the influence of gravity g)

 

[brunettegurl]

ok but that tells us what happens after it is released they're asking for velocity just before it's released from the cannon/tube

 

[rock.freak667]

ok but that tells us what happens after it is released they're asking for velocity just before it's released from the cannon/tube

When you find the resultant force, you can get the resultant acceleration...

and in the formula $v_1^2=v_0^2+2ad$

what do you need to find to get the value for v₁?

 

[brunettegurl]

we have the distance(1.50) and we now have an acceleration but would vinitial still be equal to zero??

 

[rock.freak667]

we have the distance(1.50) and we now have an acceleration but would vinitial still be equal to zero??

Yes it would be safe to assume the initial velocity as zero.

 

[brunettegurl]

thank you so much