You can't say anything about them unless their frequencies are the same.
In that case, you've already said that they're in phase, so their interference
is constructive. The resultant sound is louder than either wave alone. If their
amplitudes also happen to be the same, then the resultant sound is double
the intensity of either one alone (6 dB louder).
Answer:
m₃ = 30 kg
Explanation:
This is a problem of rotational equilibrium, let's write Newton's law for rotational equilibrium.
Let's fix our reference system in the support, the positive torques are those that create an anti-clockwise turn
Let's look for the distances to the point of support
The distance of man
x₁ = -3 m
The distance of the bar is
x₂ = L / 2 -3
x₂ = 10/2 -3
x₂ = 2 m
Remote object at the end
x₃ = L-3
x₃ = 10-3
x₃ = 7 m
They give us the mass of man (m1) and the mass of the bar (m2)
Let's write the torques
W₁ x₁ - W₂ x₂ - w₃ x₃ = 0
m₁ g 3 - m₂ g 2 - m₃ g 7 = 0
m₃ = (3m₁ -2m₂) / 7
Let's calculate
m₃ = (3 80 -2 15) / 7
m₃ = 30 kg
Answer:
2m₁m₃g / (m₁ + m₂ + m₃)
Explanation:
I assume the figure is the one included in my answer.
Draw a free body diagram for each mass.
m₁ has a force T₁ up and m₁g down.
m₂ has a force T₁ up, T₂ down, and m₂g down.
m₃ has a force T₂ up and m₃g down.
Assume that m₁ accelerates up and m₂ and m₃ accelerate down.
Sum of the forces on m₁:
∑F = ma
T₁ − m₁g = m₁a
T₁ = m₁g + m₁a
Sum of the forces on m₂:
∑F = ma
T₁ − T₂ − m₂g = m₂(-a)
T₁ − T₂ − m₂g = -m₂a
(m₁g + m₁a) − T₂ − m₂g = -m₂a
m₁g + m₁a + m₂a − m₂g = T₂
(m₁ − m₂)g + (m₁ + m₂)a = T₂
Sum of the forces on m₃:
∑F = ma
T₂ − m₃g = m₃(-a)
T₂ − m₃g = -m₃a
a = g − (T₂ / m₃)
Substitute:
(m₁ − m₂)g + (m₁ + m₂) (g − (T₂ / m₃)) = T₂
(m₁ − m₂)g + (m₁ + m₂)g − ((m₁ + m₂) / m₃) T₂ = T₂
(m₁ − m₂)g + (m₁ + m₂)g = ((m₁ + m₂ + m₃) / m₃) T₂
m₁g − m₂g + m₁g + m₂g = ((m₁ + m₂ + m₃) / m₃) T₂
2m₁g = ((m₁ + m₂ + m₃) / m₃) T₂
T₂ = 2m₁m₃g / (m₁ + m₂ + m₃)