# Newtonian Mechanics 2

• Feb 28th 2010, 02:19 AM
bobey
Newtonian Mechanics 2
An object of mass m kg is given an upward velocity of 16 m/sec from rest, 16 m above the ground. Assume that the gravity is the only force acting on it, when will the object hit the ground and at what velocity will it hit the ground? (gravity, g = 10 m/sec2)
• Mar 1st 2010, 05:36 PM
arbolis
Quote:

Originally Posted by bobey
An object of mass m kg is given an upward velocity of 16 m/sec from rest, 16 m above the ground. Assume that the gravity is the only force acting on it, when will the object hit the ground and at what velocity will it hit the ground? (gravity, g = 10 m/sec2)

Newton's second law states that $\displaystyle \vec F=m \vec a$ which is worth $\displaystyle m \vec g$ in this example.
Notice that $\displaystyle a(t)=v'(t)=r''(t)$ since it's a 1 dimensional problem. So $\displaystyle a(t)=g$.
Mathematically you have $\displaystyle g=\frac{dv}{dt}\Rightarrow g dt =dv$.
Try to take it from there. How would you go to find out $\displaystyle v(t)$?