Answer:
u=78.4m/s
Explanation:
A ball is thrown vertically upward, which is the positive direction.A little later it returns to its point of release.The ball is in the air for a total time of 8.0 s.What is its initial velocity? Neglect air resistance
from newtons equation of motion
s=ut
v=u+at
v=0 because at maximum height reached by the ball the ball stops moving
0=u-9.8*8
u=78.4m/s
u=initial velocity
v=final velocity
a=acceleration due to gravity, 9.81m/s^2
t=time it takes in air
s= distance to get to the maximum before returning
All of them will have the same density
To solve this problem, we will use the equation of motion:
v = u + at
where:
v is the final velocity = 117.72 m/sec
u is the initial velocity = zero (body starts falling from rest)
a is the acceleration of the body which is equivalent to acceleration due to gravity = 9.8 m/sec^2
t is the time that we want to calculate
Substitute with the givens in the above equation to get the time as follows:
v = u + at
117.72 = 0 + 9.8t
117.72 = 9.8t
t = 117.72 / 9.8
t = 12.0122 seconds
Answer:
20 m/s is the answer i think