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Oksanka [162]
3 years ago
12

Estimated speed of the vehicle

Physics
1 answer:
SSSSS [86.1K]3 years ago
3 0

Really, Gundy ? ! ?

The formula for the car's speed is given and discussed in the box.  The formula is

v = √(2·g·μ·d)

Then they <em>tell</em> you that μ is 0.750 , and then they <em>tell</em> you that d = 52.9 m .  Also, everybody knows that 'g' is gravity = 9.8 m/s² .

They also tell us that the mass of the car is 1,000 kg, and they tell us that it took 3.8 seconds to skid to a stop.  But we already <em>have</em> all the numbers in the formula <em>without</em> knowing the car's mass or how long it took to stop.  The police don't need to weigh the car, and nobody was there to measure how long the car took to stop.  All they need is the length of the skid mark, which they can measure, and they'll know how fast the guy was going when he hit the brakes !

Now, can you take the numbers and plug them into the formula ? ! ?

v = √(2·g·μ·d)

v = √( 2 · 9.8 m/s² · 0.75 · 52.9 m)

v = √( 777.63 m²/s²)

v = 27.886 m/s

Rounded to 3 digits, that's  <em>27.9 m/s </em>.

That's about 62.4 mile/hour .



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Novosadov [1.4K]
The first one, Climate
6 0
3 years ago
An ideal photo-diode of unit quantum efficiency, at room temperature, is illuminated with 8 mW of radiation at 0.65 µm wavelengt
nadya68 [22]

Answer:

I = 4.189 mA    V = 0.338 V

Explanation:

In order to do this, we need to apply the following expression:

I = Is[exp^(qV/kT) - 1]   (1)

However, as the junction of the diode is illuminated, the above expression changes to:

I = Iopt + Is[exp^(qV/kT) - 1]   (2)

Now, as the shunt resistance becomes infinite while the current becomes zero, we can say that the leakage current is small, and so:

I ≅ Iopt

Therefore:

I ≅ I₀Aλq / hc  (3)

Where:

I₀A = Area of diode (radiation)

λ: wavelength

q: electron charge (1.6x10⁻¹⁹ C)

h: Planck constant (6.62x10⁻³⁴ m² kg/s)

c: speed of light (3x10⁸ m/s)

Replacing all these values, we can get the current:

I = (8x10⁻³) * (0.65x10⁻⁶) * (1.6x10⁻¹⁹) / (6.62x10⁻³⁴) * (3x10⁸)

I = 4.189x10⁻³ A or 4.189 mA

Now that we have the current, we just need to replace this value into the expression (2) and solve for the voltage:

I = Is[exp^(qV/kT) - 1]

k: boltzman constant (1.38x10⁻²³ J/K)

4.189x10⁻³ = 9x10⁻⁹ [exp(1.6x10⁻¹⁹ V / 1.38x10⁻²³ * 300) - 1]

4.189x10⁻³ / 9x10⁻⁹ = [exp(38.65V) - 1]

465,444.44 + 1  = exp(38.65V)

ln(465,445.44) = 38.65V

13.0508 = 38.65V

V = 0.338 V

6 0
3 years ago
A fire truck has a searchlight with a resistance of 60 (ohm) which is placed across a 24-V battery. What is the current in this
Mariulka [41]

Answer: 0.4 Amps

Explanation:

Voltage of battery = 24 Volts

Current I = ?

Resistance of searchlight (R)= 60ohms (Ω is the symbol for ohms)

Then, apply the formula for ohms law

Voltage = Current x resistance

i.e V = I x R

24V = I x 60Ω

I = 24V / 60Ω

I = 0.4 Amps (Amps is the unit of current)

Thus, the current in the circuit is 0.4 Amps

3 0
3 years ago
An 8 kg mass moving at 8 m/s collides with a 6 kg mass
steposvetlana [31]

Answer:

10 m/s

Explanation:

Momentum before collision = momentum after collision

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

(8 kg)(8 m/s) + (6 kg)(6 m/s) = (8 kg)(5 m/s) + (6 kg) v

64 kg m/s + 36 kg m/s = 40 kg m/s + (6 kg) v

60 kg m/s = (6 kg) v

v = 10 m/s

3 0
3 years ago
Vector A has magnitude of 15.0 m/s and is 75° counter-clockwise up from the x-axis. What are the x- and y-components of the vect
LiRa [457]

Answer:

x component 3.88 y- component 14.488

Explanation:

We have given a vector A which has a magnitude of 15 m/sec which is at 75° counter-clock wise ( anti-clock wise) from x -axis which is clearly shown in bellow figure

Now x-component will be 15 cos75°=3.8822 ( as it makes an angle of 75° with x-axis )

y- component will be 15 sin 75°=14.488

For verification the resultant of x and y component should be equal to 15

So resultant =\sqrt{14.488^2+3.88^2}=15

3 0
3 years ago
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