In compressed state, a spring 3.00 meters long hanging from the ceiling has a potential energy of 4.9 joules. If the entire potential energy is used to release a ball of mass 1.2 kilograms vertically downward, then what is the kinetic energy of the ball when it reaches the ground? a
1.2 joules

b
4.9 joules

c
2.0 joules

d
6.8 joules

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here we know that ball will drop down by total distance 3.2 m

so here we know that

now using kinematics

now in the same time it will cover horizontal distance of 0.75 m

so speed of the ball will be

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