Calculating Time and Velocity in Horizontal Projectile Motion

[Awsom Guy]

Hello,
Question:
An object is projected horizontally. After t seconds it has a horizontal displacement of 10cm and a vertical diplacement of 5cm.
a) What is the value of t?
b) What is the magnitude of the initial velocity?

a) my attmept.
:( Nothing Sorry i don't get it.

 

[Syrtd]

First off, it can reasonably be assumed that we're talking about an object subject to 1 normal Earth gravity (g)?

If so, this is relatively simple since it's only over a short distance span and you don't have to junk with changing gravity like with high altitude satellite launch problems.
What you know:
a (g=9.80m/s²)
v_i (0m/s)
d (5cm down [-5cm])
t (?)
v_f (?)

1. Finding time span
The four main kinematic equations use four variables usually with three known.
We know a,v_i and d with the intent of finding t, so let's use "d=v_it+.5at²"
Since v_i equals "0" vertically, v_it drops.
Further algebra gets us "t=sqrt(2d/a)"
Crunch your numbers.

2. Finding initial horizontal velocity
Gosh... if you need help here,--- .
(By the way: "d=vt" TF "v=d/t")

 

[Awsom Guy]

Thanks, but I checked this like a month later, :D