A2-kg ball is held 4 m above the ground. relative to the ground its potential energy is:

a) 80 j
b) 32 j
c) more than 80 j
d) 8 j
e) 6 j

a) 80 J

Explanation:

The gravitational potential energy of the ball relative to the ground is:

where

m = 2 kg is the mass of the ball

g = 9.8 m/s^2 is the acceleration due to gravity

h = 4 m is the heigth of the ball above the ground

Substituting numbers into the equation,

So the correct answer is

a) 80 J

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form