Which of the following solid fuels has the highest heating value

An ambulance is rapidly approaching you at a stop light. What happens to the frequency and pitch of the sound as the ambulance d

vagabundo [1.1K]

Answer:

A )

Explanation:

This change in frequency observation occur due to doppler effect

if the wave source moves,In the time between one wave peak being emitted and the next, the source will have moved so that the shells will no longer be concentric. The wavefronts will get closer together in front of the source as it travels and will be further apart behind it. (see the graph)

when the person standing still in front of the ambulance, he will observe a higher frequency than before as the source travels towards them.

$f_(observed)=\frac{V_(wave)}{V_(wave)-V_(source)} *f_(original)$

The pitch we hear depends on the frequency of the sound wave.

A high frequency corresponds to a high pitch

as we hear a higher frequency , it makes the pitch higher too

5 0

3 years ago

Read 2 more answers

A hot-air balloon is descending at a rate of 2.1 m/s when a passenger drops a camera. If the camera is 42 m above the ground whe

zysi [14]

Answer:

a) 2.7s

b) 29 m/s

Explanation:

The equation for the velocity and position of a free fall are the following

$v=v_{0}-gt$ -(1)

$x=x_{0}+v_{0}t-gt^{2}/2$ - (2)

Since the hot-air ballon is descending at 2.1m/s and the camera is dropped at 42 m above the ground:

$v_{0}=-2.1m/s$

$x_{0}=42m$

To calculate the time which it takes to reach the ground we use eq(2) with x=0, and look for the positive solution of t:

$t = \frac{1}{84}(2.1\pm\sqrt{2.1^{2} - 4\times42\times9.81/2} )$

t = 2.71996

Rounding to two significant figures:

t = 2.7 s

Now we calculate the velocity the camera had just before it lands using eq(1) with t=2.7s

$v=-2.1-9.81*(2.71996)$

v = -28.782 m/s

Rounding to two significant figures:

v = -29 m/s

where the minus sign indicates the downwards direction

3 0

3 years ago

Sirius A has a luminosity of 26 LSun and a surface temperature of about 9400 K.What is its radius?

wlad13 [49]

Answer

Given,

Sirius A surface temperature,T = 9400 K

Sirius A luminosity,L = 26 L₀

L₀ is the luminosity of sun.

Radius of sun = 695700000 m

Temperature on sun surface = 5780 K

Luminous intensity is given by:-

$L=4 \pi R^{2} \sigma T^{4}$

Now

$\frac{L}{L_{0}}=\frac{4 \pi R^{2} \sigma T^{4}}{4 \pi R_{0}^{2} \sigma T_{0}^{4}}=26$

$\Rightarrow \frac{R^{2} T^{4}}{R_{0}^{2} T_{0}^{4}}=26$

$\Rightarrow R^{2}=26 \times \frac{R^{2} T_{0}^{4}}{T^{4}}=26 \times \frac{695700000^{2} \times 5780^{4}}{9400^{4}}$

$R=1341246640\ m=1.34 \times 10^{9}$

7 0

3 years ago

A cord is wrapped around the rim of a solid uniform wheel 0.300 m in radius and of mass 8.00 kg. A steady horizontal pull of 34.

disa [49]

Answer:

A. α = 94.4 rad/s

B. a = 28.32 m/s

C. N = 34N

D. α = 94.4 rad/s

a = 28.32 m/s

N = 44.4 N

Explanation:

part A:

using:

∑T = Iα

where T is the torque, I is the moment of inertia and α is the angular momentum.

firt we will find the moment of inertia I as:

I = $\frac{1}{2}MR^2$

Where M is the mass and R is the radius of the wheel, then:

I = $\frac{1}{2}(8 kg)(0.3 m)^2$

I = 0.36 kg*m^2

Replacing on the initial equation and solving for α, we get::

∑T = Iα

Fr = Iα

34 N = 0.36α

α = 94.4 rad/s

part B

we need to use this equation :

a = αr

where a is the aceleration of the cord that has already been pulled off and r is the radius of the wheel, so replacing values, we get:

a = (94.4)(0.3 m)

a = 28.32 m/s

part C

Using the laws of newton, we know that:

N = T

where N is the force that the axle exerts on the wheel part and T is the tension of the cord

so:

N = 34N

part D

The anly answer that change is the answer of the part D, so, aplying laws of newton, it would be:

-Mg + N +T = 0

Then, solving for N, we get:

N = -T+Mg

N = -34 + (8 kg)(9.8)

N = 44.4 N

6 0

3 years ago

What creates linear and rotary motion

Phantasy [73]

Answer:

A slider Crank Mechanism creates linear and rotary motion

Explanation:

7 0

4 years ago