A ball is thrown from ground level straight up into the air at an intitial velocity of 54 feet per second. The height of the ball t seconds after it is thrown is given by the formula h(t)=54t-16’2. How many seconds after the ball is thrown will it return to the ground

3 3/8 seconds.

Step-by-step explanation:

When it reaches the ground h = 0 so:

54t - 16t^2 = 0

16t^2 - 54t = 0

2t(8t - 27) = 0

t = 0 or t =  27/8   (we ignore the t = 0 ) so:

t =   3 3/8 seconds.

reduce the friction between its moving parts

step-by-step explanation:

in fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.

56.6

step-by-step explanation:

the ratio of the perimeters is equal to the scale.

the ratio of the areas is equal to the square of the scale.

34 / 20 = k

a / 19.6 = k²

substituting:

a / 19.6 = (34 / 20)²

a = 19.6 (34 / 20)²

a ≈ 56.6