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ycow [4]
3 years ago
6

Why can concave mirror is used in cosmetic mirror​

Physics
1 answer:
tatuchka [14]3 years ago
4 0

Answer:

"When face is placed between the concave mirror and its focus, it produces a magnified image. This enlarged image of face is helpful in makeup as even pores of skin are clearly visible."

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An incident ray of light strikes water at an angle of 30°. The index of refraction of air is 1.0003, and the index of refraction
defon

Answer: It’s A

Explanation:

22 degrees

6 0
3 years ago
Read 2 more answers
A cylindrical resistor element on a circuit board dissipates 1.2 W of power. The resistor is 2 cm long, and has a diameter of 0.
34kurt

Answer:

(a) The resistor disspates 103680 joules during a 24-hour period.

(b) The heat flux of the resistor is approximately 4340.589 watts per square meter.

(c) The fraction of heat dissipated from the top and bottom surfaces is 0.045.

Explanation:

(a) The amount of heat dissipated (Q), measured in joules, by the cylindrical resistor is the power multiplied by operation time (\Delta t), measured in hours. That is:

Q = \dot Q \cdot \Delta t (1)

If we know that \dot Q = 1.2\,W and \Delta t = 86400\,s, then the amount of heat dissipated by the resistor is:

Q = (1.2\,W)\cdot (86400\,s)

Q = 103680\,J

The resistor disspates 103680 joules during a 24-hour period.

(b) The heat flux (Q'), measured in watts per square meter, is the heat transfer rate divided by the area of the cylinder (A), measured in square meters:

Q' = \frac{\dot Q}{A} (2)

Q' = \frac{\dot Q}{\frac{\pi}{2}\cdot D^{2}+\pi\cdot D \cdot h } (3)

Where:

D - Diameter, measured in meters.

h - Length, measured in meters.

If we know that \dot Q = 1.2\,W, D = 4\times 10^{-3}\,m and h = 2\times 10^{-2}\,m, the heat flux of the resistor is:

Q' = \frac{1.2\,W}{\frac{\pi}{2}\cdot (4\times 10^{-3}\,m)^{2}+\pi\cdot (4\times 10^{-3}\,m)\cdot (2\times 10^{-2}\,m) }

Q' \approx 4340.589\,\frac{W}{m^{2}}

The heat flux of the resistor is approximately 4340.589 watts per square meter.

(c) Since heat is uniformly transfered, then the fraction of heat dissipated from the top and bottom surfaces (r), no unit, is the ratio of the top and bottom surfaces to total surface:

r = \frac{\frac{\pi}{2}\cdot D^{2}}{A} (3)

If we know that A \approx 2.765\times 10^{-4}\,m^{2} and D = 4\times 10^{-3}\,m, then the fraction is:

r = \frac{\frac{\pi}{2}\cdot (4\times 10^{-3}\,m)^{2} }{2.765\times 10^{-4}\,m^{2}}

r = 0.045

The fraction of heat dissipated from the top and bottom surfaces is 0.045.

7 0
3 years ago
A car travels 2155.0m in 195.9s. What is the car's average speed?
inna [77]

Average speed of the car is 11 m/s

Explanation:

  • Speed is calculated by the rate of change of displacement.
  • It is given by the formula, Speed = Distance/Time
  • Here, distance = 2155 m and time = 195.9 s

Speed of the car = 2155/195.9 = 11 m/s

3 0
3 years ago
A tennis player swings and hits the ball away. How does the force of the tennis racket affect the motion of the ball
defon

The force of the racket affects the ball's motion because it changes the momentum of the ball.

<h3>Impulse received by the ball</h3>

The impulse received by the ball through the racket affects the motion because it changes the momentum of the ball.

The ball which is initially at rest, will gain momentum after been hit with the racket.

J = ΔP = Ft

where;

  • J is the impulse received by the ball
  • ΔP is change in momentum of the ball
  • F is the applied force
  • t is the time of action

Thus, the force of the racket affects the ball's motion because it changes the momentum of the ball.

Learn more about impulse here: brainly.com/question/25700778

4 0
2 years ago
Which type of heat transfer causes your face to feel warm when you sit in the sun?
MA_775_DIABLO [31]

Answer:

Radiation

Explanation:

The sun radiates energy to the earth to make it warmer near the equator.

6 0
3 years ago
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