Voltage=Energy/Charge, V=E/Q
V in volts V, E in joules J, Q in coulombs C.
or
Voltage= Current×Resistance, V=IR
V in volts V, I in amperes A and R in ohms Ω
Answer:
L = 0.7 m
Explanation:
This is a resonance exercise, in this case the air-filled pipe is open at both ends, therefore we have bellies at these points.
λ / 2 = L 1st harmonic
λ = L 2nd harmonic
λ = 2L / 3 3rd harmonic
λ = 2L / n n -th harmonic
the speed of sound is related to wavelength and frequencies
v =λ f
f = v /λ
we substitute
f = v n / 2L
the speed of sound in air is v = 343 m / s
suppose that the frequency of f = 980Hz occurs in harmonic n
f₁ = v n / 2L
f₂ = v (n + 1) / 2L
f₃ = v (n + 2) / 2L
we substitute the values
2 980/343 = n / L
2 1260/343 = (n + 1) / L
2 1540/343 = (n + 2) / L
we have three equations, let's use the first two
5.714 = n / L
7.347 = (n + 1) / L
we solve for L and match the expressions
n / 5,714 = (n + 1) / 7,347
7,347 n = 5,714 (n + 1)
n (7,347 -5,714) = 5,714
n = 5,714 / 1,633
n = 3.5
as the number n must be integers n = 4 we substitute in the first equation
L = n / 5,714
L = 0.7 m
f' = frequency observed by the police car after sound reflected from the vehicle and comes back to police car = 1250 Hz
f = frequency emitted by the police car = 1200 Hz
V = speed of sound = 340 m/s
v = speed of vehicle = ?
frequency observed by the police car is given as
f' = f (V + v)/(V - v)
inserting the values in the above equation
1250 = 1200 (340 + v)/(340 - v)
v = 6.9 m/s
First you must convert Km/hr to m/s. 90 km/hr equals 25m/s (this can be done through a conversion table by plugging in the conversion values). Then you need to see what was given:
vi (initial velocity)= 0m/s
vf (final velocity= 25m/s (90km/hr)
t (time)= 10s
Next you should find an equation that requires only the values you know and gives you the value you're looking for. Sometimes that requires two equations to be used, but in this case you only need one. The best equation for this would be a=(vf-vi)/t. Finally, plug in your values (a=(25-0)/10) to get your answer which would be 2.5m/s^2. Hope this helped!
