The four equations for acceleration are obtained from the three equations of motion and from second law of motion.
Explanation:
Acceleration is defined as the rate of change of velocity with respect to time. So the change in velocity with respect to time can be determined using the three equations of motions.
So from the first equation of motion, v = u + at , we can determine the value of acceleration if time taken, final and initial velocity is known. The equation can be re-written as 
Similarly, from the second equation of motion, s = ut + 1/2 at², we can determine the equation for acceleration as 
So this is second equation for acceleration.
Then from the third equation of motion, 
the acceleration equation is determined as 
In addition to these three equation, another equation is present to determine the acceleration with respect to force from the Newton's second law of motion. F = Mass × acceleration. From this, acceleration = Force/mass.
So, these are the four equations for acceleration.
Answer:
B) Because the Space Station is constantly in free-fall around the Earth.
Explanation:
Anything that is falling experiences an upward force on them. For example when a person is going down in a lift they will experience something that is pushing them upwards. This happens due to the fact that the total acceleration the body is feeling is less than the acceleration due to graviity.
The force on a body which is falling is

Where,
m = Mass of object
g = acceleration due to gravity
a = acceleration the object is experiencing.
a = g. So, the force becomes zero and the object experiences weightlessness.
Hence, the astronauts in the space station experience weightlessness due to fact that the Space Station is constantly in free-fall around the Earth.
Answer:
Explanation:
we have to make charge inside the conductor zero because we know that electric field inside the conductor should be zero
so, the outer surface of the conductor should contain + 10 uC of charge and the inner surface contains -10 uC
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