- #1
Abukadu
- 32
- 0
Another mechanics question :) (a simpler one, I proimise!)
http://img223.imageshack.us/img223/5172/112mz7.th.jpg http://g.imageshack.us/thpix.php
As the picture shows:
M=4kg
V0=5 m/s
h=5m
F(wind)=2N
angle=15 degrees
I need to find the distance on axis x of the ball when he hits the ground.
2. The attempt at a solution
So this is how I tried to solve it..
1. I'll try to calculate the distance the ball made until he got back to the height he started with (the ball goes up a few metters, gets to a point where his speed its 0 and then drops down until he hits the ground)
-Mg - F=Ma -> -40-2=4a -> a=-10.5 m/s2 (right?)
y=yo+v0t+0.5at2
0=0+5sin15t+0.5*(-10.5)*t2
-5.25t2+1.3t=0
t=0.247s
so to that point the ball made a progress on axis x:
X1=v*t=5cos15*0.247=1.19m
Now I need to find his progress on axis x from that point, when he got back to the original height he started with and is falling down 5m.
The speed on axis y is 5sin15 m/s, so the time it will take the ball to hit the ground from that point is:
-5=0-5sin15*t+0.5*(-10.5)*t2 (did I get all the minuses right?:shy:)
5.25t2+1.3t-5=0
t=0.86s
so on axis X...
X2=v*t=5cos15*0.86=4.15m
and alltogher..
X1+X2=5.35m
is there any mistake you can tell I made alond the way?
Homework Statement
http://img223.imageshack.us/img223/5172/112mz7.th.jpg http://g.imageshack.us/thpix.php
As the picture shows:
M=4kg
V0=5 m/s
h=5m
F(wind)=2N
angle=15 degrees
I need to find the distance on axis x of the ball when he hits the ground.
2. The attempt at a solution
So this is how I tried to solve it..
1. I'll try to calculate the distance the ball made until he got back to the height he started with (the ball goes up a few metters, gets to a point where his speed its 0 and then drops down until he hits the ground)
-Mg - F=Ma -> -40-2=4a -> a=-10.5 m/s2 (right?)
y=yo+v0t+0.5at2
0=0+5sin15t+0.5*(-10.5)*t2
-5.25t2+1.3t=0
t=0.247s
so to that point the ball made a progress on axis x:
X1=v*t=5cos15*0.247=1.19m
Now I need to find his progress on axis x from that point, when he got back to the original height he started with and is falling down 5m.
The speed on axis y is 5sin15 m/s, so the time it will take the ball to hit the ground from that point is:
-5=0-5sin15*t+0.5*(-10.5)*t2 (did I get all the minuses right?:shy:)
5.25t2+1.3t-5=0
t=0.86s
so on axis X...
X2=v*t=5cos15*0.86=4.15m
and alltogher..
X1+X2=5.35m
is there any mistake you can tell I made alond the way?
Last edited by a moderator: