Atennis ball machine serves a ball vertically into the air from a height of 2 feet, with an initial speed of 130 feet per second. after how many seconds does the ball attain its maximum height?

We use the equation of motion,

.

Here, v is final velocity, u is initial velocity and a = - g (acceleration due to gravity) because ball thrown vertically into air.

At maximum height, the final velocity becomes zero, i.e v = 0.

Thus equation becomes,

 .

Given, and we take  .

Substituting these values in above equation, we get

.

Thus, to reach the maximum height the time taken by the ball is 4.05 s.

b.a device that inputs heat into a cool object

the area between the graph and the t axis