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4 years ago

Estimated speed of the vehicle

Physics

1 answer:

SSSSS [86.1K]4 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 tell you that μ is 0.750 , and then they tell 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 have all the numbers in the formula without 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 27.9 m/s .

That's about 62.4 mile/hour .

You might be interested in

Ask Your Teacher William Tell shoots an apple from his son's head. The speed of the 120-g arrow just before it strikes the apple

svlad2 [7]

Answer:

M = 0.115 kg

Explanation:

given,

mass of arrow = 120 g = 0.12 Kg

speed of arrow before it strike apple = 29.7 m/s

distance traveled by the arrow stick combination = 9.30 m

height of the son = 1.85 m

weight of the apple = ?

now,

time of flight of arrow and apple combination

using equation of motion

$h = u t + \dfrac{1}{2}gt^2$

$h = \dfrac{1}{2}gt^2$

$t = \sqrt{\dfrac{2h}{g}}$

$t = \sqrt{\dfrac{2\times 1.85}{9.8}}$

t = 0.614 s

$speed = \dfrac{distance}{time}$

$s = \dfrac{9.30}{0.614}$

s = 15.15 m/s

using conservation of momentum

m v = (M+ m) s

0.12 x 29.7 = (M+ 0.12) x 15.15

M+ 0.12 = 0.235

M = 0.115 kg

mass of apple is equal to 0.115 Kg

6 0

3 years ago

A transformer has a primary voltage of 115 V and a secondary voltage of 24 V. If the number of turns in the primary is 345, how

Nata [24]

Answer:

C. 72

Explanation:

Transformer: A transformer is an electromagnetic device that uses the property of mutual inductance to change the voltage of alternating supply.

In a ideal transformer,

Vs/Vp = Ns/Np ............................................. Equation 1

Where Vp = primary voltage, Vs = secondary voltage, Ns = Secondary turn, Np = primary turn.

Making Ns the subject of the equation,

Ns =(Vs/Vp)Np .......................................... Equation 2

Given: Vs = 24 V, Vp = 115 V, Np = 345.

Substitute into equation 2

Ns = (24/115)345

Ns = 72 turns.

Thus the number of turns in the secondary = 72 turns.

The right option is C. 72

4 0

3 years ago

Your heart pumps blood at a pressure of 100 mmHg and flow speed of 60 cm/s. At your brain, the blood enters capillaries with suc

Savatey [412]

Answer:

1.28 m

Explanation:

Generally, pressure of fluid is given by

$P=\rho g h$ where g is acceleration due to gravity, h is the height and $\rho$ is the density

Considering that the pressure for mercury is same as for blood only that the height and density of fluid are different then

$\rho_b g h_b= \rho_m g h_m$

Since g is constant, then

$\rho_b h_b= \rho_m h_m$

Making $h_b$ the subject of the formula then

$h_b=\frac {\rho_m h_m}{\rho_b}$

Where subscripts m and b denote mercury and blood respectively

Assuming density of blood is 1060 Kg/m3, density of mercury as 13600 Kg/m3 and substituting height of mercury for 0.1 m then

$h_b=\frac {13600*0.1}{1060}=1.283018868 m \approx 1.28 m$

7 0

3 years ago

The tangential acceleration of a cart moving at a constant speed in a horizontal circle is:

qaws [65]

Answer:

$a=0$ ∵ $\alpha=0\ rad.s^{-1}$

Explanation:

The tangential acceleration of a cart moving at a constant speed in a circle is:

The angular velocity is constant when the circular speed is constant.

We know that the (instantaneous) tangential velocity of such object is given by:

$v=r.\omega$

Now for angular acceleration we have a constant angular speed:

$\alpha=0\ rad.s^{-1}$

And angular acceleration is related to tangential acceleration as:

$a=r.\alpha$

$\Rightarrow a=0$

7 0

3 years ago

An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the

andrew-mc [135]

Answer:

50 W

Explanation:

Case 1

Power = V * I

100 = 220 * I

I = $\frac{100}{220}$ A

Case 2

P = V * I

P = 110 * $\frac{100}{220}$

P = 50 W

I think the answer is 50 W

Hope it helps

8 0

3 years ago