When the moon faces earth a solar eclipse happens :-)
Answer:
The value is 
Explanation:
From the question we are told that
The emitted frequency increased by 
Let assume that the initial value of the emitted frequency is

Hence new frequency will be 
Generally from Doppler shift equation we have that
![f_1 = [\frac{ v \pm v_o}{v \pm + v_s } ] f](https://tex.z-dn.net/?f=f_1%20%3D%20%20%5B%5Cfrac%7B%20v%20%5Cpm%20v_o%7D%7Bv%20%5Cpm%20%2B%20v_s%20%7D%20%5D%20f)
Here v is the speed of sound with value 
is the velocity of the sound source which is
because it started from rest
is the observer velocity So
Generally given that the observer id moving towards the source, the Doppler frequency becomes
=>
=> 
Answer:
10 N
Explanation:
Work done is the dot product of the force magnitude with distance and cosine of the angle betweenthem.
Equation to use: W=|F|*|d|*cosθ
Your unknown is the force F; You have one equation, oneunknown.
40j=(F)*(4m)*cos(0)
F=40j/4m
F=10N
Answer: Positive
Explanation:
Are you familiar with differential calculus? In a plot of position vs. time, the velocity at any given moment is the derivative at that point. A derivative is just the slope. For this plot, the slope is x/t.
Looking at t = 1s, the slope is 1/1. This means the velocity is a positive 1m/s at time equal to 1 second