Answer:
Wg is positive and WT negative.
(Letters in options are all wrongly written).
Explanation:
Remember that the work of a force is the internal product between the force and the displacement .
Since the displacement is downwards like the weight, the work done by gravity is positive, while the work done by the tension is negative since it points upwards.
Answer:
a. The sound will travel at the speed to both Jill and Jack
b. Jack
Explanation:
a. Doppler effect describes how the frequency of a sound wave changes with regards to an observer that has relative motion to the sound source;
The Doppler effect is given by the following formula;
For a sound that is moving away, as observed by Jill, we have;
For approaching sound, as observed by Jack, we have;
Where;
f = The sound wave's actual frequency
f' = The frequency of the moving sound to the observer
v = The speed of the sound wave
v₀ = The observer's velocity = 0
= The velocity of the source (the automobile honking) of the sound wave
From the above equation, we have that the speed of sound, 'v', is the same to both the source, and the observer although the frequency, and therefore, the wavelength of the sound alternatively increases or decreases
b. From the Doppler effect equation, the person who will hear the highest frequency is given by the formula for the frequency when the sound is approaching the observer, which has the lower denominator
Therefore, given that the automobile is travelling towards Jack, jack will hear the higher frequency
