Answer:
77 Ω
Explanation:
For resistors in parallel:
1/R = 1/R₁ + 1/R₂ + 1/R₃
1/26 = 1/68 + 1/93 + 1/R₃
1/R₃ = 0.013
R₃ = 77
The resistance of R₃ is 77 Ω.
Resistance = (voltage) / (current)
Resistance = (12v) / (0.33 A)
Resistance = (12/0.33) ohms
<em>Resistance = 36.4 ohms</em>
Assuming our "closed tube" is closed at only one end, then
<span> v = fλ = f*4L/n
</span><span> where "n" is the harmonic number. So
</span><span> L = nv / 4f = n*346m/s / 4*256Hz = n*0.38 m
</span> <span>Since the only option in your list that is an integer multiple of 0.38 m is 1.35 m
</span><span> I'd say that we're hearing the fourth harmonic.
answer is
</span><span>A. 1.35 m</span><span>
</span>
This one is a piece 'o cake if you know the formula for
Kinetic Energy, and impossible if you don't.
It is: KE = (1/2) (mass) (speed²) .
For this object: KE = (1/2) (30 kg) (20 m/s)²
= (1/2) (30 kg) (400 m²/s²)
= (15 x 400) (kg-m²/s²)
= 6,000 joules .