Billy tapped the ruler and it made a funny noise. Billy heard the sound because the ruler vibrated

1. Define dark matter and dark energy, and clearly distinguish between them. What types of observations have led scientists to p

Vlada [557]

Explanation:

Dark Energy is a property of the entire universe. And the universe is roughly made up of 68% of this dark energy whereas dark matter makes up 27% of the universe matter.

The influence of the dark matter shows in the individual galaxies whereas dark energy acts only on the entire universe. dark matter is responsible for the gravity effect on the plants and the heavenly bodies which produces gravity force. But the dark energy is known as the anti gravity force as it is responsible for the expansion of the universe. Dark matter attracts and produces an attractive force while dark energy repels and produces a repulsive force.

Scientist believe that they exists to account for the very fact that gravity holds all the heavenly bodies and the galaxies together. They are even responsible for the fluctuation in Cosmic Microwave background. Researchers and scientist firmly believe that all the visible matter that exists may not have enough gravitational pull to hold everything together in the galaxies. And also the expanding universe strongly proves that dark energy exists in the universe.

7 0

2 years ago

An aluminum bar 600mm long, with diameter 40mm, has a hole drilled in the center of the bar. The hole is 40mm in diameter and 10

s2008m [1.1K]

Answer:

1.228 x $10^{-6}$ mm

Explanation:

diameter of aluminium bar D = 40 mm

diameter of hole d = 30 mm

compressive Load F = 180 kN = 180 x $10^{3}$ N

modulus of elasticity E = 85 GN/m^2 = 85 x $10^{9}$ Pa

length of bar L = 600 mm

length of hole = 100 mm

true length of bar = 600 - 100 = 500 mm

area of the bar A = $\frac{\pi D^{2} }{4}$ = $\frac{3.142* 40^{2} }{4}$ = 1256.8 mm^2

area of hole a = $\frac{\pi(D^{2} - d^{2}) }{4}$ = $\frac{3.142*(40^{2} - 30^{2})}{4}$ = 549.85 mm^2

Total contraction of the bar = $\frac{F*L}{AE} + \frac{Fl}{aE}$

total contraction = $\frac{F}{E} * (\frac{L}{A} +\frac{l}{a})$

==> $\frac{180*10^{3}}{85*10^{9}} *( \frac{500}{1256.8} + \frac{100}{549.85})$ = 1.228 x $10^{-6}$ mm

6 0

2 years ago

Two light bulbs are 2.0 m apart. From what distance can these light bulbs be marginally resolved by a small telescope with a 4.5

andrezito [222]

Answer:

R = 1.2295 10⁵ m

Explanation:

After reading your problem they give us the diameter of the lens d = 4.50 cm = 0.0450 m, therefore if we use the Rayleigh criterion for the resolution in the diffraction phenomenon, we have that the minimum separation occurs in the first minimum of diffraction of one of the bodies m = 1 coincides with the central maximum of the other body

θ = 1.22 λ / D

where the constant 1.22 leaves the resolution in polar coordinates and D is the lens aperture

how angles are measured in radians

θ = y / R

where y is the separation of the two bodies (bulbs) y = 2 m and R the distance from the bulbs to the lens

$\frac{y}{R} = 1.22 \frac{ \lambda}{D}$

R = $\frac{ y \ D}{1.22 \lambda}$

let's calculate

R = $\frac{ 2 \ 0.045}{ 1.22 \ 600 \ 10^{-9}}$

R = 1.2295 10⁵ m

3 0

2 years ago

A loudspeaker produces a sound wave of frequency 50hz.

viktelen [127]

Hey mate
Here is your answer
Option A)
Explanation:
The larger the amplitude of the waves, the louder the sound. Pitch (frequency) – shown by the spacing of the waves displayed. The closer together the waves are, the higher the pitch of the sound.
Pls mark as brainliest

3 0

2 years ago

A particle travels clockwise on a circular path of diameter R, monitored by a sensor on the circle at point P; the other endpo

kotykmax [81]

We make a graphic of this problem to define the angle.

The angle we can calculate through triangle relation, that is,

$sin\theta = \frac{c}{QP}\\sin\theta = \frac{c}{R}\\\theta=sin^{-1}\frac{c}{R}$