A tuning fork of frequency 384 Hz is sounded at the same time as a guitar string. 30 beats are heard in 10 s.
a) Determine the possible frequencies of the string.
b) How many beats will be heard in 4.0 s?

You are driving directly behind a pickup truck, going at the same speed as the truck. a crate falls from the bed of the truck to the road. (a) will your car hit the crate before the crate hits the road if you neither brake nor swerve? (b) during the fall, is the horizontal speed of the crate more than, less than, or the same as that of the truck?