Answer:
I think the correct answer is period
Answer:
Option A is the correct answer.
Explanation:
Here momentum is conserved.
That is 
Substituting values

Speed of block A after collision = 10 m/s
Option A is the correct answer.
The answer is Newton's 3rd Law. The reason why is because a force is a push or a pull that acts upon an object as a results of its interaction with another object. ... These two forces are called action and reaction forces and are the subject ofNewton's third law of motion. Formally stated, Newton's third law is: For every action, there is an equal and opposite reaction.
As an airplane moves through the air, its wings cause changes in the
speed and pressure of the air moving past them. These changes result in
the upward force called lift.
The Bernoulli principle states that an increase in the speed of a fluid
occurs simultaneously with a decrease in the pressure exerted by the
fluid.
A wing is shaped and tilted so the air moving over it moves faster than
the air moving under it. As air speeds up, its pressure goes down. So
the faster-moving air above exerts less pressure on the wing than the
slower-moving air below. The result is an upward push on the wing—lift!
An object can be at rest and still be in motion because the earth is always in motion.