Question

Mary throws a plastic disc to her friend. Her friend catches the disc six seconds after Mary throws it. The table shows the height of the disc at one-second intervals.

A 2-column table with 7 rows. The first column is labeled Time (seconds) with entries 0, 1, 2, 3, 4, 5, 6. The second column is labeled Height (feet) with entries 3, A, 6, 7, 6, 4, B.
Assuming that the throw represents projectile motion, what are the missing values in the table?

A = 5, B = 3
A = 4, B = 0
A = 4, B = 3
A = 5, B = 0

Answer 1

A = 4, B = 3.

Reason: For projectile motion the height is a quadratic in time, so it is symmetric about its vertex. The maximum height 7 occurs at t = 3, so heights at times equidistant from 3 are equal: h(1)=h(5)=4 and h(0)=h(6)=3.