D. Free fall
Explanation:
An object is said to be in free fall when there is only one force acting on the body, which is the force of gravity.
Near the Earth's surface, the force of gravity acting on a body is given by
F = mg
where
m is the mass of the body
g is the acceleration of gravity (its value is
)
The direction of this force is downward (towards the Earth's centre).
If we apply Newton's second law on an object in free-fall, we can find its acceleration. In fact, we have:

And substituting F,

So, every object in free-fall accelerates at
towards the ground.
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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:
Explanation:
Momentum is the mass of a moving body times its velocity. It can be transferred from one object to another
Answer:
Explanation:
Given
mass 
Force 
door knob is located at a distance of r=0.8 m from axis
Angular acceleration of door 
Torque 
where I=moment of inertia


4x + 4 < 4x + 3 (expand it)
4 < 3 (cancel 4x on both sides)
Since 4 < 3 is not true there is no solution.
Answer: NO SOLUTION.