Question

Guided Practice

Use the vertical motion formula h = –16t2 + vt + c.


A child tosses a ball upward with a starting velocity of 10 ft/s from a height of 3 ft. Substitute the values into the vertical motion formula and let h = 0. Use the quadratic formula to solve for t. How long is the ball in the air?


A.
0.8 s


B.
0.8 s or –0.2 s


C.
0.2 s

Answer 1

0.8 s

Explanation:

I got it right in grandpoint.

Answer 2

t = -0.22secs and 0.85secs

Explanation:

Given the expression

h = –16t² + vt + c.

If a child tosses a ball upward with a starting velocity of 10 ft/s from a height of 3 ft, then;

v = 10, c = 3

Since we are to let h = 0, then the equation becomes:

0 = –16t² + 10t + 3

Multiply through by a minus sign

16t² - 10t - 3 = 0

Factorize the reulting expression:

t = -(-10)±√(-10)²-4(16)(-3)/2(16)

t = 10±√100+192/32

t = 10±√292/32

t = 10±17.09/32

t = 10-17.09/32 and 10+17.09/32

t = -7.09/32 and 27.09/32

t = -0.22secs and 0.85secs