While running around the track at school, Milt notices that he runs due East on the 100m homestretch and due West on the 100m ba
2 answers:
The correct answer is
A) The homestretch and backstretch have velocities with the same magnitude only.
Explanation:
Velocity is a vector - it means it consists of:
1) A magnitude: called speed, it is given by the ratio between the total distance covered, d, and the time taken, t:
2) A direction: the direction of motion
In this example, we see that the homestretch and the backstretch have same speed, because the same distance (100 m) is covered in the same time interval (100 m), however the direction is different (the homestretch is due East, while the backstretch is due West). So, the correct answer is
A) The homestretch and backstretch have velocities with the same magnitude only.
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Answer:
a) I = 3.63 W / m² , b) I = 0.750 W / m²
Explanation:
The intensity of a sound wave is given by the relation
I = P / A = ½ ρ v (2π f )²
I = (½ ρ v 4π² s_{max}²) f²
a) with the initial condition let's call the intensity Io
cte = (½ ρ v 4π² s_{max}²)
I₀ = cte s² f₀²
I₀ = cte 10 6
If frequency is increase f = 2.20 10³ Hz
I = constant (2.20 10³) 2
I = cte 4.84 10⁶
let's find the relationship of the two quantities
I / Io = 4.84
I = 4.84 Io
I = 4.84 0.750
I = 3.63 W / m²
b) in this case the frequency is reduced to f = 0.250 10³ Hz and the displacement s = 4 s or
I = cte (f s)²
I = constant (0.250 10³ 4)²
I = cte 1 10⁶
the relationship
I / Io = 1
I = Io
I = 0.750 W / m²
12 V is the f.e.m. 
of the battery. The potential difference that is applied to the motor is actually the fem minus the voltage drop on the internal resistance r:
this is equal to the voltage drop on the resistance of the motor R:
so we can write:
and using
and 
we can find the current I:
this is equal to the voltage drop on the resistance of the motor R:
so we can write:
and using