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Jobisdone [24]
3 years ago
8

Heidi (39 kg) is walking her tiny chihuahua, Chaxi (5.60 kg), on the sidewalk. To encourage Chaxi along, Heidi pulls forward wit

h a force of 9.55 N. Identify the correct reaction force in response to Heidi’s action force.
a. The friction is less than 660 N since the beam can be moved at a constant velocity.
b. There is no friction acting on the beam since it is accelerating.
c. The friction is equal to 660 N since the beam is not accelerating.
d. The friction is greater than 660 N since the beam is not in equilibrium.
Physics
1 answer:
Ivan3 years ago
4 0

Answer:

The correct reaction force in response to Heidi's action force is:

c. The friction is equal to 660 N since the beam is not accelerating.

Explanation:

Heidi's action force does not affect the beam.  Since friction resists the sliding or rolling of one solid object over another, there is no friction acting on the beam, in this respect.  The reaction force is what makes the dog to move because it acts on it.  According to Newton's Third Law of Motion, forces always come in action-reaction pairs.  This Third Law states that for every action force, there is an equal and opposite reaction force.  This means that the dog exerts some force on Heidi, as he pulls it "forward with a force of 9.55 N."

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A stationary police car emits a sound of frequency 1240 HzHz that bounces off of a car on the highway and returns with a frequen
lara [203]

Answer:

frequency =  1475.45 Hz

Explanation:

given data

frequency f1 = 1215 Hz,

frequency f2 = 1265 Hz

police car moving vp = 25.0 m/s

solution

speed of sound u = 343 m / s

speed of the other car = v

when the police car is stationary

the frequency the other car receives is

f2 =  f1  ×  \dfrac{u+v}{u}      ................1

and

the frequency the police car receives is

 f2 =  f1  ×  \dfrac{u}{u-v}      ..................2

now from equation 1 and 2

\frac{f2}{f1} = \dfrac{u+v}{u-v}

 \frac{1275}{1240} = \frac{u+v}{u-v}

v =\frac{1275-1240}{1275+1240}\times 343  

v = 4.77 m/s

and

frequency the other car receives is  

f2 = f1 ×   \dfrac{u+v}{u-vp}       ......................3

and

the frequency the police car receives is

f2 = f1 ×  \dfrac{u+vp}{u - v}       .......................4

now we get

f2 = f1 ×  \dfrac{(u+v)(u + vp)}{(u-v)(u-vp)}      

f2 =    1240\times \frac{(343+4.77)(343+25)}{(343-4.77)(343-25)}        

f2 =  1475.45 Hz

 

4 0
4 years ago
You have 4.9 g of an unknown substance. To identify the substance, you decide to measure its specific heat and find that it requ
kifflom [539]

The unknown substance can be lithium, which has a specific heat capacity of approximately 3.5 J/gK.

Explanation:

When heat energy is supplied to a certain substance, the temperature of the substance increases according to the equation:

Q=mC_s \Delta T

where

Q is the amount of energy supplied

m is the mass of the sample

C_s is the specific heat capacity of the substance

\Delta T is the change in temperature

In this problem, we have

m = 4.9 g is the mass

Q = 668.85 J is the specific heat capacity

\Delta T = 39 K is the change in temperature

Solving for C_s, we find the specific heat capacity of the substance:

C_s = \frac{Q}{m\Delta T}=\frac{668.85}{(4.9)(39)}=3.5 J/gK

Looking at tables of specific heat capacity, we can see that the unknown substance can be lithium, which has a specific heat capacity of approximately 3.5 J/gK.

Learn more about specific heat capacity:

brainly.com/question/3032746

brainly.com/question/4759369

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3 0
3 years ago
Electromagnets are created by?
AysviL [449]
A coil of insulated wire around an iron core 
7 0
4 years ago
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How much heat is needed to raise the temperature of 50.0 g of water by 25.0°C
love history [14]

Answer:

Explanation:

In order to be able to solve this problem, you will need to know the value of water's specific heat, which is listed as

c

=

4.18

J

g

∘

C

Now, let's assume that you don't know the equation that allows you to plug in your values and find how much heat would be needed to heat that much water by that many degrees Celsius.

Take a look at the specific heat of water. As you know, a substance's specific heat tells you how much heat is needed in order to increase the temperature of

1 g

of that substance by

1

∘

C

.

In water's case, you need to provide

4.18 J

of heat per gram of water to increase its temperature by

1

∘

C

.

What if you wanted to increase the temperature of

1 g

of water by

2

∘

C

? You'd need to provide it with

increase by 1

∘

C



4.18 J

+

increase by 1

∘

C



4.18 J

=

increase by 2

∘

C



2

×

4.18 J

To increase the temperature of

1 g

of water by

n

∘

C

, you'd need to supply it with

increase by 1

∘

C



4.18 J

+

increase by 1

∘

C



4.18 J

+

...

=

increase by n

∘

C



n

×

4.18 J

Now let's say that you wanted to cause a

1

∘

C

increase in a

2-g

sample of water. You'd need to provide it with

for 1 g of water



4.18 J

+

for 1 g of water



4.18 J

=

for 2 g of water



2

×

4.18 J

To cause a

1

∘

C

increase in the temperature of

m

grams of water, you'd need to supply it with

for 1 g of water



4.18 J

+

for 1 g of water



4.18 J

+

,,,

=

for m g of water



m

×

4.18 J

This means that in order to increase the temperature of

m

grams of water by

n

∘

C

, you need to provide it with

heat

=

m

×

n

×

specific heat

This will account for increasing the temperature of the first gram of the sample by

n

∘

C

, of the the second gram by

n

∘

C

, of the third gram by

n

∘

C

, and so on until you reach

m

grams of water.

And there you have it. The equation that describes all this will thus be

q

=

m

⋅

c

⋅

Δ

T

, where

q

- heat absorbed

m

- the mass of the sample

c

- the specific heat of the substance

Δ

T

- the change in temperature, defined as final temperature minus initial temperature

In your case, you will have

q

=

100.0

g

⋅

4.18

J

g

∘

C

⋅

(

50.0

−

25.0

)

∘

C

q

=

10,450 J

Rounded to three sig figs and expressed in kilojoules, t

Explanation:

3 0
3 years ago
Read 2 more answers
A 5.0-kg centrifuge takes 95 s to spin up from rest to its final angular speed with constant angular acceleration. A point locat
stellarik [79]

Answer:

(a) 17.37 rad/s^2

(b) 12479

Explanation:

t = 95 s, r = 6 cm = 0.06 m, v = 99 m/s, w0 = 0

w = v / r = 99 / 0.06 = 1650 rad/s

(a) Use first equation of motion for rotational motion

w = w0 + α t

1650 = 0 + α x 95

α = 17.37 rad/s^2

(b) Let θ be the angular displacement

Use third equation of motion for rotational motion

w^2 = w0^2 + 2 α θ

1650^2 = 0 + 2 x 17.37 x θ

θ = 78367.87 rad

number of revolutions, n = θ / 2 π

n = 78367.87 / ( 2 x 3.14)

n = 12478.9 ≈ 12479

4 0
3 years ago
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