Which element is likely to be the most reactive? bromine (Br) chlorine (Cl) fluorine (F) iodine (I)
2 answers:
You might be interested in
(6) first choice: the frequency appears higher and wavelength is shorter.
The car approaches a stationary observer and so the sound will appear to have shorter wavelength. This creates an effect of its siren to sound with higher frequency than it would do if both were stationary.
(7) The Doppler formula for frequency in the case of a stationary observer and source approaching it is as follows:
The wavelength is then
The third choice "0.80m; 431Hz" is correct
Answer:
-4892 J
Explanation:
The work done by friction is equal to the difference in mechanical energy of the car between the bottom of the loop (point A) and the top of the loop (point B).
The mechanical energy of the car at point A is
where
is the mass of the car
is the speed at point A
is the height of the car at point A (zero because it is at the bottom of the loop)
Substituting into the equation, we find
The mechanical energy of the car at point B is
where
is the mass of the car
is the speed at point B
(twice the radius) is the height of the car at point B, at the top of the loop
Substituting into the equation, we find
So, the work done by friction is
And the work is negative because it is done against the motion of the car.