Calculating the Impact of a Hammer on a Lawn

[loka]

Homework Statement

A hammer slides 21 m down the side of the roof inclined at 60 deg. above the horizontal, and falls down to the lawn 11m below the edge of the roof.

How far away from the wall will this hammer impact with the lawn?

m = 1 kg
mu = 0.23

Homework Equations

The Attempt at a Solution

Fgx = mg sin 60
= (1) (9.8)sin60
= 8.487N

Ff = UFn = 1.127 N

Fnet = Fgx - Ff = 8.487 - 1.127 = 7.36 N

Fnet = ma
a = Fnet/m = 7.36 m/s^2

to find t sub y = 11

y = yo + voyt - 1/2gt^2
0 = 4.9t^2 + 15.23t - 11
t = -15.23 +- (15.23^2 - 4(4.9) (-11)))^sq root

t = -15.23 +- (15.23^2 - 4(4.9) (-11)))^sq root / 2 (4.9)

t = -15.23+- (447.5529)^1/2/ 9.8

then t = 0.06004

sub t = 0.604 into x = Vxt
x = 17.582cos60 (0.604)
x = 5.3 m

5.3 m away from the wall

?? i rly doubt this is rite...??

 

[rl.bhat]

It appears to be correct.