# Finding instantaneous velocity of objects in projectile motion

1. Mar 16, 2008

### Suzan

1. The problem statement, all variables and given/known data
No air resitance
Initial speed 8 m/s
inst. time at 3 s

Find instantaneous velocity at 3s.

Components of displacement:
dx= 24
dy= 44

2. Relevant equations

d=v1t+(1/2)a(t)^2 or other kinematics equations

3. The attempt at a solution

I tried to find the components of the velocity using the components of the displacement (d/t=v). But both my answer and angle of direction were wrong. How do i do this?

2. Mar 16, 2008

### rock.freak667

So dx and dy are those values at t=3?
If so consider Vertical motion:
$s=ut+\frac{1}{2}at^2$

where u is the initial vertical velocity. Sub t=3 in there and get u. and well you know how to get the horizontal component (v=d/t as you stated before)