45% of 20
20 times 0.45
= 9
The answer is 9
The value of x is 2 because we can compare like terms
Here we're applying a basic physics rule for vertical motion where the only pull on the object is gravity.
This rule has the form
h(t) = h + v t + (1/2)a*t^2
o o
To adapt this rule to this particular question replace h with 0, as the
o
upward path of the object begins at 0 ft. Replace v with +15 ft/sec.
o
Replace "a" with (-32.2 ft/(sec^2); this is the acceleration due to gravity.
Then we have the following, with the label F(t):
F(t) = 0 + (15 ft/sec)t + (1/2)(-32.2 ft)/(sec^2), or
F(t) = 15t - 16.1t^2. Thus, Choice D is correct.
Please note: To avoid confusion, please use " ^ " to denote exponentiation:
F(t) = -16t^2 + 15t
