Physics problem, please help!!!?
A person sees a lightning bolt pass close to an airplane that is flying in the distance. The person hears thunder 5.0 s after seeing the bolt and sees the airplane overhead 10 s after hearing the thunder. the speed of sound is air is 1100 ft/s.
a.) find the distance of the airplane from the person at the instant of the bolt. (Neglect the time it takes the light to travel from the bolt to the eye.)
b.) assumin gthe plane travels with a constant speed toward the person, find the velocity of the airplane.
c.) look up the speed of light in air and defend the approximation used in part (a).
Please anwer in detail so I may understand how to solve. THANKS!
Comments
a) you have a duration (5 seconds) and a speed (1100 ft/second). If you multiply them together, you'll get the distance, in feet, to the point where the lightning bolt and airplane were located.
b) the airplane took (5 + 10 seconds) to get overhead. Take the distance in a), and divide by this time, to get the speed of the airplane in ft/second.
c) The speed of light is 983,571,100 ft/second. If you divide the distance in a) by this speed, you'll get a very short time, much, much less than 5 seconds.
I have found treating the units by themselves to help me find a direction in a problem:
a) [seconds] * [feet / second] = [feet]
b) [feet] / [seconds] = [feet/second]
c) [feet] / [feet/second] = [seconds]
... you can see how the units cancel...