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taurus [48]
2 years ago
3

A small light source located 1 m in front of a 1-m2 opening illuminates a wall behind. If the wall is 1 m behind the opening (2

m from the light source), the illuminated area covers 4 m2. How many square meters are illuminated if the wall is 3 m from the light source? 5 m? 10 m?
Physics
1 answer:
AlekseyPX2 years ago
5 0

Answer:

3 m : 9 m² ; 5m: 25 m² ; 10 m : 100 m²

Explanation:

If we assume that the light source behaves like as a point source, the light emitted by the source propagates through the space in all directions equally, which means that it obeys an inverse square law, as a consequence of our universe being 3D.

So, if at 1 m from the source, the illumination covers 1m², at 2m, it will cover 4 m², at 3m 9m², at 5 m 25 m², and at 10 m, 100 m2.

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A flywheel of mass M is rotating about a vertical axis with angular velocity ω0. A second flywheel of mass M/5 is not rotating a
Contact [7]

Answer:

0.83 ω

Explanation:

mass of flywheel, m = M

initial angular velocity of the flywheel, ω = ωo

mass of another flywheel, m' = M/5

radius of both the flywheels = R

let the final angular velocity of the system is ω'

Moment of inertia of the first flywheel , I = 0.5 MR²

Moment of inertia of the second flywheel, I' = 0.5 x M/5 x R² = 0.1 MR²

use the conservation of angular momentum as no external torque is applied on the system.

I x ω = ( I + I') x ω'

0.5 x MR² x ωo = (0.5 MR² + 0.1 MR²) x ω'

0.5 x MR² x ωo = 0.6 MR² x ω'

ω' = 0.83 ω

Thus, the final angular velocity of the system of flywheels is 0.83 ω.

5 0
2 years ago
A man can row at 6kmhr in still water and want to cross a river to a position exactly opposite his starting point. If the river
Lina20 [59]

Answer:

if the river is 5km wide and is flowing at 4km/hr. eastwards find by scale ... Find either by scale drawing or by calculation (1) the direction in which he must ... He could row his boat directly across the river to point C and then run to B, or he ... A man who can swim at 5km/h in still water swims towards the east to cross arriver.

Explanation:

3 0
2 years ago
Which statement correctly describes the relationship between frequency and wavelength?
Len [333]
The relationship between the frequency and wavelength of a wave is given by the equation:

v=λf, where v is the velocity of the wave, λ is the wavelength and f is the frequency. 

If we divide the equation by f we get:

λ=v/f

From here we see that the wavelength and frequency are inversely proportional. So as the frequency increases the wavelength decreases. 

So the second statement is true: As the frequency of a wave increases, the shorter the wavelength is.  
3 0
2 years ago
Read 2 more answers
A sister spins her brother in a circle of radius R at angular speed wi. Then the sister decreases her angular speed
Igoryamba

Answer:

The change in the centripetal acceleration of the brother,

                               Δa = V₂²/R - V₁²/R

Explanation:

Given data,

A sister spins her brother in a circle of radius, R

The angular velocity of the brother, ω₁ = V₁/R

The angular velocity of the brother, ω₂ = V₂/R

The centripetal acceleration is given by the relation

                                 a = V²/R

Therefore change in the centripetal acceleration of the brother,

                              Δa = V₂²/R - V₁²/R                                    

6 0
2 years ago
A student decides to spend spring break by driving 50 miles due east, then 50 miles 30 degrees south of east, then 50 miles 30 d
stira [4]

Answer:600 miles, 12

Explanation: The movement described in the question exhibits that of a polygon. Exhibiting a constant distance and angle with only varying direction until the starting point is reached.

The sum of exterior angles of a polygon = 360 degrees.

Exterior angle of a polygon = (360 ÷ number of sides)

Therefore,

Number of sides = 360 ÷ exterior angle

Exterior angle = 30 degrees

Hence,

Number of sides = 360 ÷ 30 = 12 sides

Since distance traveled of 50 miles is the same for each displacement ;

Total displacement = distance traveled * number of sides

Total displacement = 50 * 12 = 600 miles.

5 0
2 years ago
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