Imagine that you replace the block in the video with a happy or sad ball identical to the one used as a pendulum, so that the sad ball strikes a sad ball and the happy ball strikes a happy ball. the target balls are free to move, and all the balls have the same mass. in the collision between the sad balls, how much of the balls' kinetic energy is dissipated?

a) none of it
b) all of it
c) half of it
they refer to a "sad ball" as a ball which doesn't bounce at all. example, if you dropped the ball on the ground it would simply stop (like clay) --> so it's a completely inellastic collision.

the answer is half of it, but could someone explain how we arrive to this conclusion? like maybe using some formulas?

c)as speed changes, wavelength and frequency change.

everything changes!

answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.

seeing the graph would

the answer is 12 as i may remember

: )