Question

Rock 1 Rock 2
Mass (kg) 2.5 25
Height of Fall (m) 78.4 78.4
Time to Fall (s) 4.0 ?
Based on this data, how many seconds will it take rock 2 to fall?
A. 1.6 seconds
B. 0.4 seconds
C. 4.0 seconds
D. 40 seconds

Answer 1

C. 4.0 seconds.

Time of fall depends on height and gravitational acceleration, not mass. Use s = 1/2 g t^2:
t = sqrt(2s/g) = sqrt(2·78.4 / 9.8) = sqrt(16) = 4.0 s.