I wish people would stop saying its a simple problem. Simple is so relative. And it''s considerably harder if you don''t know the constant acceleration formula (you know the one I mean), you start going into calculus to derive the damn thing. (or messy algebra).
Y ^ V0=4 m/sec | N k=0.2 | /\ --->V0 | | | | | f<----* -------------------|------------------>X | \/ mg
( I dont know why the drawing doesnt shows right at the post, it does at edit mode :/ )
N is the counter force working on the body N=mg
1st Law of Niuton on Y axis ( no acceleration ) ============================= the sum of all forces = masa * acceleration N-mg=0 since you havent specified the masa of the body i presume its 1 and g=9.8 round it up to 10, g=10 and since the gravity working against axis Y g=-10
N=1*-10=-10 N=-10
2nd Law of Niuton on X axis =========================== f=ma
f=k*N=0.2N=0.2*-10=-2 -2=1*a a=-2 // the acceleration on the x axis is -2
Now you got all you need to solve this problem
X(t)=X0+V0x*t+a*t^2/2
(a) X(t)=0+4*t-2*t^2/2
the speed equation: V(t)=V0+ax*t when the body will stop its speed will be 0 V(t)=0 0=4-2*t t=2sec // after 2 sec the body will stop now we put t=2sec in equation (a) X(t=2sec)=4*2-2*4/2=8-4=4 meters
So the bodey will stop after 4 meters
[edited by - spree on December 5, 2003 1:48:52 AM]