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4 years ago

Can someone answer these?

Physics

1 answer:

natita [175]4 years ago

4 0

Short Answer

3: C

4: D

Problem Three

Remark

Somewhere we ought to be told that this is the Doppler Effect. I have never done a problem using this formula, so I think I'm doing it correctly, but no guarantees. My guess is that the frequency increases as it comes towards you and decreases as it moves away from you. I think that is correct.

Formula

Givens

f' = observed frequency
f = actual frequency
v = velocity of sound or light waves.
vo = velocity of observer (in both cases 0)
vs = velocity of source.

f' = (v + vo) * f / (v - vs)

Solution

v = 3*10^8 m/s
f' = 1.1 f
f = f
vo = 0 We are standing still while all this is going on.
vs = ???

f'/f = 1.1

1.1 = (3*10^8 + 0 ) / (3*10^8 - vs)

3.3*10^8 - 1.1*vs = 3*10^8

3.3*10^8 - 3*10^8= 1.1 vs

0.3 * 10^8 = 1.1 vs

2.73 * 10^7 = vs

The closest answer is 3.00 * 10^7 which is C

Problem Four

Here what is happening is that you are looking for the frequency resulting from a wave moving towards you at 1/2 the speed of sound. You are not moving.

Givens

v = v
vs = 1/2 v
f ' = ?
f = 1000 hz
vo =0

f' = v/(v - 1/2v) * 1000

f' = v/ (1/2 v) * 1000

f' = 2 * 1000

f' = 2000 which is D

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3 years ago

Calculate the amount of heat needed to raise the temperature of 200g of ice from-30°C 50C water. (C = .5 for ice, C 1 for water,

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Answer: The amount of heat needed is 29000 Cal.

Explanation:

The process involved in this problem are:

$(1):H_2O(s)(-30^oC)\rightarrow H_2O(s)(0^oC)\\\\(2):H_2O(s)(0^oC)\rightarrow H_2O(l)(0^oC)\\\\(3):H_2O(l)(0^oC)\rightarrow H_2O(l)(50^oC)$

Now, we calculate the amount of heat released or absorbed in all the processes.

For process 1:

$q_1=mC_{p,s}\times (T_2-T_1)$

where,

$q_1$ = amount of heat absorbed = ?

m = mass of ice = 200 g

$T_2$ = final temperature = $0^oC$

$T_1$ = initial temperature = $-30^oC$

Putting all the values in above equation, we get:

$q_1=200g\times 0.5Cal/g^oC\times (0-(-30))^oC=3000Cal$

For process 2:

$q_2=m\times L_f$

where,

$q_1$ = amount of heat absorbed = ?

m = mass of water or ice = 200 g

$L_f$ = latent heat of fusion = 80 Cal/g

Putting all the values in above equation, we get:

$q_2=200g\times 80Cal/g=16000Cal$

For process 3:

$q_3=m\times C_{p,l}\times (T_{2}-T_{1})$

where,

$q_3$ = amount of heat absorbed = ?

m = mass of water = 200 g

$T_2$ = final temperature = $50^oC$

$T_1$ = initial temperature = $0^oC$

Putting all the values in above equation, we get:

$q_3=200g\times 1Cal/g^oC\times (50-0)^oC=10000Cal$

Calculating the total heat absorbed, we get:

$Q=q_1+q_2+q_3$

$Q=3000+16000+10000=29000Cal$

Hence, the amount of heat needed is 29000 Cal.

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4 years ago

A 600kg car is at rest , and then accelerates to 5n/s what is the original kinetic energy?

lubasha [3.4K]

M = 600 kg
u = 0 (as the car was at rest initially)
v = 5 m/s
Initial kinetic energy = ½mu²
= ½×600×0
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4 years ago

I dont understand how to find the blanks

Amiraneli [1.4K]

The forces are:

$F_{grav} = 98,000 N$ , down

$F_{net} = 80,000 N$ , down

$F_{air}=18,000 N$ , up

Explanation:

We start by finding the force of gravity on the elephant, $F_{grav}$ , which is given by

$F_{grav}=mg$ (downward)

where

m = 10,000 kg is the mass of the elephant

$g=9.8 m/s^2$ is the acceleration of gravity

Substituting,

$F_{grav}=(10,000)(9.8)=98,000 N$

Now we know that the net acceleration of the elephant is

$a_{net}=8.0 m/s^2$ downward

We can now use Newton's second law:

$F_{net}=ma_{net}$

where $F_{net}$ is the net force on the elephant. Substituting, we find

$F_{net}=(10,000)(8.0)=80,000 N$

and it also acts downward, since it has the same direction as the acceleration.

Finally, we can write the net force on the elephant as

$F_{net}=F_{grav}-F_{air}$

where the force of gravity acts downward, while the air resistance ( $F_{air}$ acts upward. The net force also acts downward, so it has the same sign of gravity.

Substituting:

$F_{net}=80,000 N\\F_{grav}=98,000 N$

And solving, we find the air resistance:

$F_{air}=F_{grav}-F_{net}=98,000-80,000 = 18,000 N$ (upward)

Learn more about forces and Newton laws of motion:

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#LearnwithBrainly

4 0

4 years ago