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2 years ago

Why do stars twinkle

1 answer:

4 0

As light from a star races through our atmosphere, it bounces and bumps through the different layers, bending the light before you see it. Since the hot and cold layers of air keep moving, the bending of the light changes too, which causes the star's appearance to wobble or twinkle.

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Forces affect motions in living and nonliving things. In a human, swallowed food moves down the esophagus into the stomach, even

valina [46]

Answer:

figured it out its d the last one

4 0

2 years ago

In which situation is work not being done?

almond37 [142]

work done =W = F.d = F d cosФ (Ф is angle between force F and displacement d) If a body/object is moving on a smooth surface (friction-less surface ) .There is no force acting on that body. F=0 so W=FdcosФ= (0)dcosФ ⇒ W=0

Now if a body is facing some amount of force but under the action of force there is no displacement covered. d=0 so W =FdcosФ= F(0)cosФ ⇒W=0

example: A person is applying a force on rigid wall but wall remains at rest there is no displacement occurs in wall.

The third term upon which work done dependent is angle between force and displacement i.e Ф. If Ф=90° then W= FdcosФ= Fdcos90⇒ W=0 ( as cos 90°=0)

5 0

2 years ago

A truck traveling at a constant speed of 28 m/s passes a more slowly moving car. The instant the truck passes the car, the car b

choli [55]

Answer:

the velocity of car when it passes the truck is u = 16.33 m/s

Explanation:

given,

constant speed of truck = 28 m/s

acceleration of car = 1.2 m/s²

passes the truck in 545 m

speed of the car when it just pass the truck = ?

time taken by the truck to travel 545 m

time = $\dfrac{distance}{speed}$

time = $\dfrac{545}{28}$

time =19.46 s

velocity of the car when it crosses the truck

$S = ut + \dfrac{1}{2}at^2$

$545= u\times 19.46 + \dfrac{1}{2} \times 1.2 \times 19.46^2$

u = 16.33 m/s

the velocity of car when it passes the truck is u = 16.33 m/s

5 0

3 years ago

Fill-in-the-blank test questions measure ________; matching concepts with their definitions measures ________.

Ulleksa [173]

Test questions measure recall; matching concepts with their definitions measures recognition.

<u>Explanation: </u>

According to Psychology our brain remembers everything what we learn but the understanding and remembering the right answer for the right question needs training and understanding ability. So in order to enhance the ability of recalling and recognizing among the students, the concept of test questions and matching with definitions are used in curricular activities.

As the students will be learning different terms, definitions, methods and different subjects, they should be able to distinguish among different definitions as well as they should recall the things they have learnt. So the answers for the test questions will help to recall the topics learnt by the students while the matching concept will help the students to recognize each definition with their terms.

6 0

2 years ago

A block with a mass of 9.00 kg is pulled at a constant speed across a horizontal tabletop with a spring scale. The scale reads 6

snow_tiger [21]

Answer:0.69

Explanation:

Coefficient of kinetic friction=f/R=61.8/90=0.69

7 0

3 years ago

Why do stars twinkle​

Why do stars twinkle