Force and motion

[Cantworkit]

Homework Statement

In throwing a 200-g ball, one's hand exerts a constant upward force of 9.4 N for 0.32 s. How high does the ball rise after leaving the hand? Book answer is 7.2 m.

Homework Equations

F = ma
v = v0 + at
y - y0 = v^2/2g

The Attempt at a Solution

Fup + Fdn = Fnet
aup = Fup/m = 9.4 kg-m/s^2/200g*1000g/kg = 47 m/s^2
v0 = at = 47m/s^2 * 0.32s = 15 m/s
y-y0 = v0^2/2g = (15)^2/2 * 9.8 = 11.5 m

 

[Tedjn]

Which should you use: a_up or a_net?