How do I calculate the efficiency of motor

What is the intensity of a sound with a sound intensity level (SIL) 67 dB, in units of W/m^2?

vfiekz [6]

Answer:

The intensity of sound (I) = 3.16 x 10⁻⁶ W/m²

Explanation:

We have expression for sound intensity level (SIL),

$L=10log_{10}\left ( \frac{I}{I_0}\right )$

Here we need to find the intensity of sound (I).

$L=10log_{10}\left ( \frac{I}{I_0}\right )\\\\log_{10}\left ( \frac{I}{I_0}\right )=0.1L\\\\\frac{I}{I_0}=10^{0.1L}\\\\I=I_010^{0.1L}$

Substituting

L = 67 dB and I₀ = 10⁻¹² W/m² in the equation

$I=I_010^{0.1L}=10^{-12}\times 10^{0.1\times 65}\\\\I_0=10^{-12}\times 10^{6.5}=10^{-5.5}=3.16\times 10^{-6}W/m^2$

The intensity of sound (I) = 3.16 x 10⁻⁶ W/m²

8 0

3 years ago

A 2.24x10^3 kg car slows down uniformly from 20.0 m/s to a stop (assume constant acceleration) via a braking force of 8.41x10^3

melisa1 [442]

Answer:

Explanation: 139 m

4 0

3 years ago

9. A Veggie meatball with v = 5.0 m/s rolls off a 1.0 m high table. How long does it take to hit the floor if no one sneezes? Wh

Paha777 [63]

By Considering the vertical distance and both vertical and horizontal final velocity, the time t = 0.45 s and Velocity V = 6.7 m/s

Given that a Veggie meatball with v = 5.0 m/s rolls off a 1.0 m high table.

Height h = 1.0 m

As the ball rolls off the table, it will be fallen under gravity. Where

g = 9.8 m/ $s^{2}$

Initial vertical velocity $u_{y}$ = 0

Initial horizontal velocity $u_{x}$ = 5 m/s

Considering the vertical distance, the formula to use to calculate the time will be;

h = ut + 1/2g $t^{2}$

1 = 0 + 1/2 x 9.8 $t^{2}$

1 = 4.9 $t^{2}$

$t^{2}$ = 1/4.9

t = $\sqrt{0.204}$

t = 0.45 seconds

It takes 0.45 seconds to hit the floor if no one sneezes.

To calculate its velocity when it hits the floor, we will need to calculate for both vertical and horizontal final velocity and find the resultant velocity of the two.

Vertical component

$V_{y}$ = $U_{y}$ + gt

$V_{y}$ = 0 + 9.8(0.45)

$V_{y}$ = 4.41 m/s

Horizontal component

$V_{x}$ = $u_{x}$ + at

but a = 0

$V_{x}$ = 5 m/s

Final velocity V = $\sqrt{5^{2} + 4.41^{2} }$

V = 6.67 m/s

Therefore, it will hit the floor at a velocity of 6.7 m/s

Learn more here: brainly.com/question/5063616

8 0

3 years ago

Why is specific heat important

Ad libitum [116K]

Hey!!

here is your answer >>>

Specific heat is the amount of heat required to raise the temperature of a unit substance!. The most common example!. The specific heat of water is 1 !. And, lot of plays and animals live under the water and if the specific heat of the water would be low, then the aquatic organisms would die, but the specific heat is high and it is hard for the sun to increase the temperature!.

Hope my answer helps!

3 0

3 years ago

An electron moves in a region where the magnetic field is uniform and has a magnitude of 80 μT. The electron follows a helical p

sladkih [1.3K]

Answer:

3.4 x 10⁴ m/s

Explanation:

Consider the circular motion of the electron

B = magnetic field = 80 x 10⁻⁶ T

m = mass of electron = 9.1 x 10⁻³¹ kg

v = radial speed

r = radius of circular path = 2 mm = 0.002 m

q = magnitude of charge on electron = 1.6 x 10⁻¹⁹ C

For the circular motion of electron

qBr = mv

(1.6 x 10⁻¹⁹) (80 x 10⁻⁶) (0.002) = (9.1 x 10⁻³¹) v

v = 2.8 x 10⁴ m/s

Consider the linear motion of the electron :

v' = linear speed

x = horizontal distance traveled = 9 mm = 0.009 m

t = time taken = $\frac{2\pi m}{qB}$ = $\frac{2\pi (9.1\times 10^{-31})}{(1.6\times 10^{^{-19}})(80\times 10^{-6})}$ = 4.5 x 10⁻⁷ sec

using the equation

x = v' t

0.009 = v' (4.5 x 10⁻⁷)

v' = 20000 m/s

v' = 2 x 10⁴ m/s

Speed is given as

V = sqrt(v² + v'²)

V = sqrt((2.8 x 10⁴)² + (2 x 10⁴)²)

v = 3.4 x 10⁴ m/s

6 0

3 years ago