a ball is thrown vertically into the air and when it returns after an interval of 2 seconds, it is caught. which one of the following statements is true if the acceleration due to gravity is 10 m/s/s and air resistance can be neglected?

a. the acceleration at the top of its flight is 10 m/s/s upwards.
b. the acceleration at the top of its flight is 0 m/s/s.
c. the time taken for the descending motion does not equal the time taken for the ascending motion.
d. the acceleration after it leaves the hand is 10 m/s/s downwards.

D. The acceleration after it leaves the hand is 10 m/s/s downwards

Explanation:

Vertical Throw

When an object is thrown upwards, it describes a special type of motion ruled only by gravity.  

When the ball is launched, it has its maximum speed upwards. The acceleration of gravity is always the same because it's a constant value near our planet's surface. The object starts to lose speed since the acceleration of gravity is pointed downwards and makes the object stop in the mid-air at its maximum height, where the speed is zero. Then, the object starts to fall and regain speed, this time downwards until it reaches back the launching point at the very same speed it was launched, but in the opposite direction.

The time it takes to reach its maximum height is the same it takes to return to the catching point, 2 seconds later.  

With all these concepts in mind, we state that:

D. The acceleration after it leaves the hand is 10 m/s/s downwards  

The other options are not correct   because:

A. The acceleration is never upwards  

B. The acceleration is never 0  

C. Both times are equal

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