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Aliun [14]
4 years ago
14

An important news announcement is transmitted by radio waves to people sitting next to their radios 42 km from the station and b

y sound waves to people sitting across the newsroom 9.26 m from the newscaster. Taking the speed of sound in air to be 343 m/s, who receives the news first?
Physics
1 answer:
Alik [6]4 years ago
8 0

Answer:

news will reach to the listener who are 42 km apart

Explanation:

given,

distance of the radios from the station = 42 Km

speed of the sound in the air = 343 m/s

distance of the people = 9.26 m

time =\dfrac{distance}{speed}

time taken by the signal to reach to the radio

speed of the electromagnetic wave to reach to the people

speed of electromagnetic wave = 3 × 10⁸ m/s

t =\dfrac{42000}{3 \times 10^8}

t = 1.4 μs

time taken to reach to the people

time =\dfrac{distance}{speed}

t =\dfrac{9.26}{343}

t = 27 ms

time taken by the station to radio is less.

hence, news will reach to the listener who are 42 km apart

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A mine car, whose mass is 440kg, rolls at a speed of 0.50m/s on ahorizontal track, as the drawing shows. A 150kg chunk of coalha
ella [17]

Answer: 0.56 m/s

Explanation:

hello, there is 25° inclination angle for the chute in the drawing. Thankfully, I know this problem. The conservation of momentum.

so there are X and Y components for the momentum in this problem. The Y component is not conserved as when the coal gets in the cart, the normal force exerted by the surface reduces it to 0.

Now, the X component is definitely conserved here.

so you have the momentum of the cart which is 440*0.5 added to the momentum of the chunk which is 150*0.8*cos(25°), that is the momentum before the coupling between the objects. Afterwards both objects will have the same velocity, so we write the equation like this:

440*0.5 + 150*0.8*cos(25) = 440*v_{final} + 150*v_{final} \\ => 220+120*cos(25) = (440+150)v_{final} => v_{final} = \frac{220+120*cos(25)}{590}  = 0.56 m/s

3 0
3 years ago
Conduction is greater in solids .explain in your own words Why?
yan [13]

Explanation:

because conduction takes place in objects whose particles are close/touching each other therefore conduction happens in solid as liquid and gas paricles are not close to each other

4 0
2 years ago
One end of a horizontal spring with force constant 76.0 N/m is attached to a vertical post. A 5.00-kg can of beans is attached t
Jobisdone [24]

Answer:

a. The speed is 2.39 m/s

b. The acceleration of the block is 10.2\frac{m}{s^{2} }

Explanation:

First, we have to do the energy balance where we consider two states, the first where the spring remains still and the second when it is stretched 0.400m:

K_{1} +U_{1}+W_{ext}=K_{2}+U_{2}\\K_{1}=0\\U_{1}=\frac{1}{2} kx^{2} _{1} =0\\W_{ext}=FΔx=(0.400m)\\

W_{ext}=20.4 Nm

U_{2} =\frac{1}{2} kx^{2} =\frac{1}{2} (76.0N/m)0.400^{2}=6.08Nm\\k_{2} =\frac{1}{2}mv^{2} _{2}  \\\frac{1}{2} mv^{2} _{2}=W_{ext}-U_{2}\\v_{2}=\sqrt{\frac{W_{ext}-U_{2}}{m} } \\v_{2}=\sqrt{\frac{20.4Nm-6.08Nm}{2.5kg} } \\v_{2}=2.39 \frac{m}{s}

To determine, the acceleration we solve the following equation for a:

F=ma\\a=\frac{F}{m} =\frac{51.0N}{5.00kg}\\a=10.2\frac{m}{s^{2} }

8 0
4 years ago
A lightweight string is wrapped several times around the rim of a small hoop. If the free end of the string is held in place and
MariettaO [177]

Answer:

Explanation:

Let T be the tension

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mg -T = ma , m is mass of the hoop . a is linear acceleration of CG of hoop .

For rotational motion of hoop

Torque by tension

T x R ,      R is radius of hoop.

Angular acceleration be α,

Linear acceleration a = α R

So TR = I  α

= I  a / R

a = TR² / I

Putting this value in earlier relation

mg -T = m TR² / I

mg = T ( 1 + m R² / I )

T = mg / ( 1 + m R² / I )

mg / ( 1 + R² / k² )

Tension is less than mg or weight because denominator of the expression is more than 1.

5 0
3 years ago
Sam has been working to improve his muscular fitness. He jumps rope and trains with weights. What will most likely be the result
const2013 [10]
Increased Bone Density
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4 years ago
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