To solve this problem we will apply Newton's second law. The second law says that mass by acceleration is equivalent to the Force exerted on a body. Mathematically this
Here,
m = mass
a = Acceleration
The ball flies through the air under the effect of gravity only. Therefore the acceleration is due to gravity, we have that
Then,
Replacing
The negative sign implies that the force acting on the ball is in the downward direction that is towards the negative y direction.
Answer:
Explanation:
The best way to do this is to remember the rule about the halfway mark in a parabolic path. At a trajectory's half way point in its travels, it will be at its max height. To get the total time in the air, we take that time at half way and double it. Here's what we know that we are told:
initial velocity is 20 m/s
Here's what we know that we are NOT told:
a = -9.8 m/s/s and
final velocity is 0 at an object's max height in parabolic motion.
We will use the equation:
where v is final velocity and v0 is initial velocity. Filling in:
0 = 20 + (-9.8)t and
-20 = -9.8t so
t = 2 seconds. The stone reaches its max height 2 seconds after it is thrown; that means that after another 2 seconds it will be on the ground. Total air time is 4 seconds.