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4 years ago

Why is ‘black’ the absence of light? And because of this, why are we still able to see black print on a paper?

Physics

1 answer:

kvv77 [185]4 years ago

8 0

Answer:

Black is the result of absorbing all colors with different wavelengths. No light is reflecting off it that we can see. So we can see it in white because as far as our eyes, there is just enough contrast in the light against the white for the print to be visible.

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On one of the shelves in your physics lab is displayed an antique telescope. A sign underneath the instrument says that the tele

Vesna [10]

Answer:

The focal length fe of the eyepiece is 2.86 cm

Explanation:

Since we are given the telescope's magnification and the length of the tube, we can use the expressions

M = f_o/fe (1) and

l = f_o + fe (2)

where

M is the telescope's magnification
l is the length of the tube
fe is the focal length of the eye-piece

Rearranging equation (2) to make f_o the subject of the formula, we get

f_o = l - fe

Substituting the above equation into equation (1) we get

M = (l - fe)/fe ⇒ fe = l/(M +1)

⇒ fe = 60/(20 + 1)

⇒ fe = 2.86 cm

4 0

4 years ago

Twoâ cars, 405 kilometersâ apart, begin driving toward each other on aâ long, straight highway. one car travels 70 kilometers pe

mart [117]

The space between the cars closes at (70+65)=135 km/hr. They collide in (405/135)=3 hours after they start moving. In 3 hours, the canary covers (100km/hr x 3)= 300 km.

8 0

4 years ago

A pool is to be filled with 60 m3 water from a garden hose of 2.5 cm diameter flowing water at 2 m/s. Find the mass flow rate of

stealth61 [152]

Answer:

Time= 6.12*10^4s

mass flow rate m=0.98kg/s

Explanation:

Given

Volume= 60m^3

diamter= 2.5cm= 0.025m

radius= 0.0125m

area A= πr^2

area A= 3.142*0.0125^2

area A= 4.9*10^-4m^2

the velocity of the flow 2m/s

volume flow rate

V=vA

V=2* 4.9*10^-4

V=9.82*10^-4 m^3/s

Time taken to fill the pool

time= volume/volume flow rate

time= 60/9.82*10^-4

time= 6.12*10^4s

Mass flow rate

m= density *volume flow rate

Assuming the density of water to be 997kg/m^3

m= 997*9.82*10^-4

m=0.98kg/s

6 0

3 years ago

A spring with k = 53 N/m hangs vertically next to a ruler. The end of the spring is next to the 18 cm mark on the ruler. If a 2.

Anarel [89]

Answer:

1.07 m

Explanation:

x = Compression of the spring

k = Spring constant = 53 N/m

Initial length = 18 cm

P = Kinetic energy

K = Kinetic energy

At the lowest point of the mass the energy conservation is as follows

$P_{ig}+P_{is}+K_i=P_{fg}+P_{fs}+K_f\\\Rightarrow mgx+0+0=mgx+\frac{1}{2}kx^2\\\Rightarrow x=\frac{2mg}{k}\\\Rightarrow x=\frac{2\times 2.4\times 9.81}{53}\\\Rightarrow x=0.89\ m$

At its lowest position the mark on the ruler will be

$x_f=0.18+0.89\\\Rightarrow x_f=1.07\ m$

The spring line will end up at 1.07 m

4 0

3 years ago

The diagram below shows two bowling balls, A and B, each having a mass of 7.0 kg, placed 2.00 m apart between their centers.

AVprozaik [17]

Answer:

F = 1.63 x 10⁻⁹ N

Explanation:

Complete question is as follows:

The diagram below shows two bowling balls, A and B, each having a mass of 7.0 kg, placed 2.00 m apart between their centers. Find the magnitude of Gravitational Force?

Answer:

The gravitational force is given by Newton's Gravitational Law as follows:

F = Gm₁m₂/r²

where,

F = Gravitational Force = ?

G = Universal Gravitational Constant = 6.67 x 10⁻¹¹ N.m²/kg²

m₁ = m₂ = mass of each ball = 7 kg

r = distance between balls = 2 m

Therefore,

F = (6.67 x 10⁻¹¹ N.m²/kg²)(7 kg)(7 kg)/(2 m)²

F = 1.63 x 10⁻⁹ N

7 0

3 years ago