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kobusy [5.1K]
3 years ago
13

Leila drove to the mountains last weekend. There was heavy traffic on the way there, and the trip took 10 hours. When Leila drov

e home, there was no traffic and the trip only took 7 hours. If her average rate was 18 miles per hour faster on the trip home, how far away does Leila live from the mountains?
Physics
1 answer:
9966 [12]3 years ago
5 0

Answer:

420 miles

Explanation:

Since distance is speed times time taken, you get two conditions:

\left \{ {{d=v*10} \atop {d=(v+18)*7}} \right.

Easiest way to solve it is to set the two condition equal - she's coming and going from the same place after all - and you get 10v=(v+18)*7\\10v=7v+3*6*7\\3v=3*6*7 \\v=42 Replace in either equation and you'll get d=420

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A penny rides on top of a piston as it undergoes vertical simple harmonic motion with an amplitude of 4.0cm. If the frequency is
aniked [119]

1) At the moment of being at the top, the piston will not only tend to push the penny up but will also descend at a faster rate at which the penny can reach in 'free fall', in that short distance. Therefore, at the highest point, the penny will lose contact with the piston. Therefore the correct answer is C.

2) To solve this problem we will apply the equations related to the simple harmonic movement, hence we have that the acceleration can be defined as

a = -\omega^2 A

Where,

a = Acceleration

A = Amplitude

\omega= Angular velocity

From a reference system in which the downward acceleration is negative due to the force of gravity we will have to

a = -g

-\omega^2 A = -g

\omega = \sqrt{\frac{g}{A}}

From the definition of frequency and angular velocity we have to

\omega = 2\pi f

f = \frac{1}{2\pi} \sqrt{\frac{g}{A}}

f = \frac{1}{2\pi} \sqrt{\frac{9.8}{4*10^{-2}}}

f = 2.5Hz

Therefore the maximum frequency for which the penny just barely remains in place for the full cycle is 2.5Hz

6 0
3 years ago
Magnet A doesn't have its poles labeled, but Magnet B has a clearly labeled north and south pole. If the
dusya [7]

Answer:

D:   The side of Magnet A that's attracted to Magnet B's south pole must be Magnet A's north pole

Explanation:

D:  The side of Magnet A that's attracted to Magnet B's south pole must be Magnet A's north pole because

1) opposite poles attract each other

2) similar poles repel each other

3)magnetic lines of force start at the north pole and end at the south pole

4 0
3 years ago
Read 2 more answers
When you drink cold water, your body must expend metabolic energy in order to maintain normal body temperature (37° C) by warmi
Gelneren [198K]

Answer:

7.72 Liters

Explanation:

normal body temperature = T_body =37° C

temperature of ice water = T_ice =0°c

specfic heat of water = c_{water} =4186J/kg.°C

if the person drink 1 liter of cold water mass of water is = m = 1.0kg

heat lost by body is Qwater =mc_{water} ΔT

                                           = mc{water} ( T_ice - T_body)

                                             = 1.0×4186× (0 -37)

                                             = -154.882 ×10^3 J

here negative sign indicates the energy lost by body in metabolic process energy expended due to brisk - hour long walk is Q_{walk} = 286 kilocalories

            = 286×4186J

so number of liters of ice water have to drink is

n×Q_{water} =Q_{walk}                                                                        n= Q_{walk}/ Q_{water}

= 286×4186J/154.882×10^3 J

 = 7.72 Liters

7 0
3 years ago
Read 2 more answers
Which mixture can be separated based on differences in particle size of the components? Check all that apply.
slamgirl [31]
It’s not Cereal and Milk, carbonated drinks, and smoky air
6 0
3 years ago
A hiker starts at point P and walks 2.0 km due east and then walks at an angle of 30 degrees north of east for 1.4 km.
olchik [2.2K]

Answer:

The magnitude of the hiker’s displacement is 2.96 km

Explanation:

Let the initial displacement of the hiker, = x = 2km

the final displacement of the hiker, = y = 1.4 km

The resultant of the two vectors, According to Pythagorean theorem is the vector sum of the two vectors.

R' = x' + y'

Check the image uploaded for solution;

8 0
3 years ago
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