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Zielflug [23.3K]
4 years ago
7

Physical Science Pre-Test 2020-2021 Question: 1-10 The distance between Earth and the Moon was determined by measuring the time

it took for light waves from Earth to travel to the Moon and back. Why was it not possible to use sound waves for this experiment Sound waves must move through a substance Sound waves would change frequency on the return to Earth Sound waves move too slowly for the technique to be accurate Sound waves move more slowly in Earth's atmosphere than in space​
Physics
1 answer:
LiRa [457]4 years ago
5 0

Answer:

Option A - Sound waves must move through a substance

Explanation:

Unlike light waves, sound waves must travel through a medium/substance for such a medium to vibrate and then produce sound.

As a matter of fact sound can't travel through empty space.

Thus, looking at the options given, the correct one is:

Sound waves must move through a substance which is Option A

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A truck moving at 13.3 m/s hits a concrete wall. As a result of the collision, a 6-kg wrench moves forwards and strikes the wall
Naddik [55]

Answer:

Explanation:

The velocity of the wrench must be equal to the velocity of the truck . So momentum of the wrench before it hits the wall

= mv = 6 x 13.3 = 79.8 kg m /s

If resisting force of wall be F , impulse on the wrench = F x time

= F x .07

Impulse = change in momentum of the wrench = mv - 0 = mv = 79.8 kgm/s

So F x .07 = 79.8

F = 1140 N .

8 0
3 years ago
Consider the force field and circle defined below. F(x, y) = x2 i + xy j x2 + y2 = 121 (a) Find the work done by the force field
kirza4 [7]

Answer: the work done by the force is 0

Explanation:

F (x², xy)

121 = 11²

so R = x² + y² = 11²

p = x². Q = xy

Δp/Δy = 0, ΔQ/Δx

using Green's theorem

woek = c_∫F.Δr = R_∫∫ ΔQ/Δx - Δp/Δy) ΔA

=  (x² + y² = 121)_∫∫ yΔA

now let x = rcosФ, y = rsinФ

ΔA = rΔrΔФ

so r from 0 to 11

and Ф from 0 to 2π

= 0_∫^2π   0_∫^11  rsinФ × rΔrΔФ

= 0_∫^2π SinФΔФ   0_∫^11  r²Δr

= [ -cosФ]^2π_0 [r³/3]₀¹¹ = ( -cos2π + cos0) (11³/3) = 0

therefore the work done by the force is 0

3 0
4 years ago
An object that is dropped from a height H falls with a constant acceleration of g. The final
GuDViN [60]

The height need to change by 4 to double the final velocity.

<h3>Final velocity of the object</h3>

The final velocity of an object during a free fall is related to maximum height of fall as given the equation below.

v = √2gh

v² = 2gh

v²/h = 2g

v₁²/h₁ = v₂²/h₂

when v₂ = 2v₁, change in height is calculated as;

h₂ = h₁v₂²/v₁²

h₂ = (h₁ (2v₁)²) / (v₁)²

h₂ = 4h₁v₁² / v₁²

h₂ = 4h₁

Thus, the height need to change by 4 to double the final velocity.

Learn more about final velocity here: brainly.com/question/25905661

#SPJ1

4 0
2 years ago
The direction that an induced current flows in a circuit is given by
AURORKA [14]

Answer:

Lenz's law

Explanation:

it  states that induced emf  of  different polarities induces a current whose magnetic field opposes the change in magnetic flux through the coil  in order to ensure that original flux is maintained through the coil  when current flows in it.

according to Faraday' s law of electromagnetic induction

Where -ve sign due to lenz's law

Emf is the induced voltage also known as electromotive force

N is the number of loops.

dϕ Change in magnetic flux.

dt Change in time.

8 0
3 years ago
What is Force!????!?​
spin [16.1K]

A force is a push or pull upon an object resulting from the object's interaction with another object.

4 0
3 years ago
Read 2 more answers
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