Homework Help: Physics

Posted by Sejul on Saturday, February 11, 2012 at 7:11pm.

A projectile of mass 1.350 kg is shot straight up with an initial speed of 22.0 m/s.
(a) How high would it go if there were no air friction?
(b) If the projectile rises to a maximum height of only 17.8 m, determine the magnitude of the average force due to air resistance.

I got the "a" correct with 24.69 m

I need help with part B. I used
F(17.8) = 1/2 (1.350)(22.0)^2 = 18.35 N and it was wrong. I need help with the correct equation to use. Thank you.

Physics - drwls, Saturday, February 11, 2012 at 7:20pm
(Avg. resistance force) x distance = LOSS of energy, not the initial kinetic energy

Energy loss = Initial KE - M*g*17.8m
= 326.7 J - 235.5 J = 91.2 J

Fav = 5.1 N

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