An object is thrown vertically from a height of #7 m# at # 3 m/s#. How long will it take for the object to hit the ground?
1 Answer
Explanation:
We're asked to find the time
As soon as the object is let go, it is in a state of freefall, and the kinematics equations can predict its motion, such as its maximum height reached, time of flight, etc.
To find this time, we can use the equation
For this equation,

The height
#y# is ground level, which I'll call#0# #"m"# 
The initial
#y_0# is#7# #"m"# 
The initial
#y# velocity#v_(0y)# is#3"m"/"s"# 
The time
#t# is when it is at height#y = 0# , which is what we're trying to find 
The
#y# acceleration#a_y# is equal to#g# , which is#9.8"m"/("s"^2)#
Plugging in our known values, we have
Using the quadratic formula:
Thus, the object will strike the ground after