
<u>Explanation:</u>
Velocity of B₁ = 4.3m/s
Velocity of B₂ = -4.3m/s
For perfectly elastic collision:, momentum is conserved

where,
m₁ = mass of Ball 1
m₂ = mass of Ball 2
v₁ = initial velocity of Ball 1
v₂ = initial velocity of ball 2
v'₁ = final velocity of ball 1
v'₂ = final velocity of ball 2
The final velocity of the balls after head on elastic collision would be

Substituting the velocities in the equation

If the masses of the ball is known then substitute the value in the above equation to get the final velocity of the ball.
Answer:
C. The facial feedback theory
Explanation:
The facial feedback theory as postulated by William James and connects back to the famous Charles Darwin talks about how facial expressions stimulate our emotional state of being. Based on this theory, the emotional experiences we have are determined by the looks on our faces.
According to the question, smiling at an event makes you enjoy it is an example of what the The facial feedback theory is explaining. Furthermore, smiling, which is a facial expression causes or stimulates an emotional state of enjoyment in that event.
I do believe that the answer is D.
Hope this is right! Have a great day! :-)
As it is given that Bulk modulus and density related to velocity of sound

by rearranging the equation we can say

now we need to find the SI unit of Bulk modulus here
we can find it by plug in the units of density and speed here

so SI unit will be

SO above is the SI unit of bulk Modulus