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Papessa [141]
3 years ago
8

After the first few seconds of a race, a runner runs at the same speed until she approaches the finish line, at which point she

increases her speed. Which statement best explains why she only did work at the beginning and end of the race? (Ignore work done against air resistance and friction.)
Physics
1 answer:
Rzqust [24]3 years ago
5 0

DUJFIOflmC VANWSER

EXPLANTATION

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erma4kov [3.2K]
<h2>Explanation:</h2><h3>3. </h3>

When light bounces back, it is <em>reflected</em>. (That's why you see your <em>reflection</em> in a mirror.) When light is bent from the path it is taking, it is <em>refracted</em>. The only answer choice that makes correct use of these terms is the third choice:

  • Part of the ray is <em>refracted</em> into ray B; part of the ray is <em>reflected</em> as ray R.

_____

<h3>4.</h3>

The index of refraction is the ratio of the sine of the angle of incidence to the sine of the angle of refraction. Both angles are measured from the normal to the surface. The angle of refraction here is 12.5° less than the angle of incidence, 44°, so is 31.5°. Then the index of refraction of the medium is ...

  n = sin(44°)/sin(31.5°) = 0.69466/0.52250 = 1.3299 ≈ 1.33

  • none of the offered choices is correct. The closest is 1.34.
8 0
3 years ago
If a car can go from 0 to 60 km/h in 8.0 seconds, what would be its final speed after 5.0 seconds if its starting speed were 50
dmitriy555 [2]

Answer:

This question assumes that the car accelerates at the same rate as when it went from 0 to 60km/h

24.29m/s or 87.4km/h

Explanation:

Let's find the acceleration of the car:

let vi=0, vf=60km/h (16.67m/s), Δt = 8.0s

a = (vf-vi)/Δt

a = (16.67m/s-0)/8.0

a = 2.08m/s^2

Now we can use this acceleration to find vf in the second part:

50km/h is 13.89m/s

a = (vf-vi)Δt

vf = aΔt + vi

vf = 2.08m/s^2*5.0+13.89m/s

vf = 24.29m/s (87.4km/h)

3 0
2 years ago
The latent heat of vaporization of a substance is the amount of energy associated with doing which of the following to 1 kg of t
mr Goodwill [35]
Converting it from liquid to gas
6 0
3 years ago
Read 2 more answers
A spring gun is made by compressing a spring in a tube and then latching the spring at the compressed position. A 4.87-g pellet
Serga [27]

Complete Question

The complete question is shown on the first uploaded image

Answer:

The work done by the spring is = 0.27 J

Explanation:

Force = torque × length

Given

F = 9.13 N

length (L) = 5.91 cm  = 0.0591 m                         [Note 1 m = 100 cm ]

considering the formula above

          9.13 = k * 0.0591    where k denotes torque

          k = 154.48\ N/m

Energy Stored  = \frac{1}{2} k x^2

                          = \frac{1}{2} * 154.48 * (0.0591)^2

                         = 0.27J  

8 0
3 years ago
Sully uses a battery and a coil of wire to create an electromagnet. Using the same materials, if he wants to increase the streng
garik1379 [7]
An electromagnet is a type of magnet in which the magnetic field is produced using the current. The simplest form of an electromagnet is a wire wrapped around in a coil.
The strength of magnetic field of such magnet is given with this equation:
B=\frac{NI\mu}{L}
Where N is the number of loops in the coil, I is the strength of the current flowing through the coil, L is the length of the coil, and \mu is <span>permeability of the electromagnet core material.
From this equation, we can see that increasing both the current and number of loops will increase the strength of the magnet.
Both BLANKS should be Increase. When you use the additional battery you will have more voltage and more voltage means more electricity.</span>
5 0
3 years ago
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