You drop a pencil from your desk, which is 1 meter above the floor. How long does it take for the pencil to hit the floor? How f
1 answer:
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Answer:
a) 4.2m/s
b) 5.0m/s
Explanation:
This problem is solved using the principle of conservation of linear momentum which states that in a closed system of colliding bodies, the sum of the total momenta before collision is equal to the sum of the total momenta after collision.
The problem is also an illustration of elastic collision where there is no loss in kinetic energy.
Equation (1) is a mathematical representation of the the principle of conservation of linear momentum for two colliding bodies of masses and
whose respective velocities before collision are
and
;
where and
are their respective velocities after collision.
Given;
Note that =0 because the second mass
was at rest before the collision.
Also, since the two masses are equal, we can say that so that equation (1) is reduced as follows;
m cancels out of both sides of equation (2), and we obtain the following;
a) When , we obtain the following by equation(3)
b) As stops moving
, therefore,