Answer:
C. It is radiation leftover from the Big Bang
Speed= distance/ time so distance = speed * time= 28 * 20= 560m .. so the answer is 560m.. l hope it helped :)
Answer:
Star A is brighter than Star B by a factor of 2754.22
Explanation:
Lets assume,
the magnitude of star A = m₁ = 1
the magnitude of star B = m₂ = 9.6
the apparent brightness of star A and star B are b₁ and b₂ respectively
Then, relation between the difference of magnitudes and apparent brightness of two stars are related as give below: 
The current magnitude scale followed was formalized by Sir Norman Pogson in 1856. On this scale a magnitude 1 star is 2.512 times brighter than magnitude 2 star. A magnitude 2 star is 2.512 time brighter than a magnitude 3 star. That means a magnitude 1 star is (2.512x2.512) brighter than magnitude 3 bright star.
We need to find the factor by which star A is brighter than star B. Using the equation given above,



Thus,

It means star A is 2754.22 time brighter than Star B.
Considering that the book is moving with constant speed, the force applied by Anna must be the same that the friction force:

If we clear the previous equation:
<h3>Question 1</h3>
Answer
option C) velocity
Explanation
acceleration = Δv ÷ Δt
<h3>Question 2</h3>
Answer
option C) m/s²
Explanation
Δv ÷ Δt
= m/s ÷ s
= m/s x 1/s
= m/s²
<h3>Question 3</h3>
Answer
option B) velocity has both direction and speed.
That is why velocity can be negative but speed can not and velocity is rate of change of displacement where as speed is rate of change of distance.