Answer:
v = 0.92 c
Explanation:
Here, we will use the time dilation formula from Einstein's theory of relativity to find the speed of traveling of the friend:

where,
v = speed of traveling = ?
c = speed of light
t = time of return = 10 years
t₀ = time passed on earth = 4 years
Therefore,

<u>v = 0.92 c</u>
Answer:
No, the acceleration is not always zero.
Explanation:
It does not mean that the acceleration of the particle is zero.
The velocity of wave is different from the velocity of particle.
The acceleration of wave is different from the acceleration of particle.
the acceleration of the particle is given by

where, w is the angular frequency and y is the displacement from the mean position.
So, the acceleration is zero at mean position only and it varies as the position changes.
Answer: C) 200 N
Explanation:
The force
is defined as:

Where:
is the mass of the object
is the acceleration
Then:

Finally:

Hence, the correct option is C.
Wind farms, solar collectors, and nuclear power plants generate no pollution.
But wind farms make noise, wind and solar are both hazardous to birds, and there's no known means of disposing of nuclear plant waste that's completely safe.