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Arturiano [62]
3 years ago
12

Physical changes (2 points)

Physics
1 answer:
xxTIMURxx [149]3 years ago
5 0
Physical changes do not change the identity of the substance. Heat causes chemical reactions. You cannot see chemical changes with the naked eye. The identity of a substance changes like when you burn paper, from paper it turns into ash and produces smoke, which are products from the chemical reactions. 
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Suppose you wanted to start a fire using sunlight and a mirror. Which of the following statements is most accurate? A) It would
Maru [420]
<h2>Answer: B) It would be best to use a concave mirror, with the object to be ignited positioned halfway between the mirror and its center of curvature. </h2>

Explanation:

To start a fire it is more optimal to use a concave mirror than a plane mirror. This is because the concave mirror allows concentrating sunlight at a point (the focal point) on an object that acts as fuel and ignite the fire there.

For this it is necessary the object to be  positioned between the center of curvature of the mirror and the mirror (its focus). Thus the rays of the Sun, when converging on the focus, will heat the object and make it burn.

Hence, the correct option is B.

6 0
4 years ago
Does anyone know what the Diaphragm on the microscope does?
steposvetlana [31]

Answer:

Diaphragm or Iris: Many microscopes have a rotating disk under the stage. This diaphragm has different sized holes and is used to vary the intensity and size of the cone of light that is projected upward into the slide.

Explanation:

6 0
4 years ago
A boat can move at a constant velocity of 8 km/h in still water. How long will it take for the boat to move 24 km?
Elis [28]

Answer: D.) 3hrs

Explanation:

Given the following :

A boat can move at a constant velocity of 8 km/h; How long will it take for the boat to move 24 km

Recall:

Velocity = Displacement / time

For the boat to travel a distance of 24 km at a constant velocity of 8km /hr

Time taken = Displacement(distance moved) / velocity

Time taken = 24km / 8kmhr^-1

Tine taken = 3hrs

4 0
3 years ago
A Doppler radar sends a pulse at
Rufina [12.5K]

Answer:

Explanation:

The problem is based on the concept of Doppler's effect of em wave .

Expression for apparent frequency can be given as follows

n = N x (V - v ) / ( V + v )

n is apparent frequency , N is real frequency , V is velocity of light  and v is velocity of cloud.

n = 6 x 10⁹ ( 3 x 10⁸ - 8.52 ) / ( 3 x 10⁸ + 8.52 )

= 6 x 10⁹ ( 3 x 10⁸ ) ( 3 x 10⁸ + 8.52 )⁻¹

= 6 x 10⁹ ( 3 x 10⁸ ) ( 3 x 10⁸)⁻¹ ( 1  + 8.52/3 x 10⁸ )⁻¹

= 6 x 10⁹ ( 1  - 8.52/3 x 10⁸ )

= 6 x 10⁹    - 6 x 10⁹x  8.52/ (3 x 10⁸ )

= 6 x 10⁹  1  - 170 .

So change in frequency = 170 approx.

7 0
3 years ago
Read 2 more answers
Radiation, conduction, and convection are methods of energy transfer. Of these methods, radiation is the only one in which energ
8_murik_8 [283]

C. Space.

Radiation is a process by which heat energy is transferred through space.

4 0
3 years ago
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