Answer:
av=0.333m/s, U=3.3466J
b.

Explanation:
a. let
be the mass of block A, and
be the mass of block B. The initial velocity of A,
-The initial momentum =Final momentum since there's no external net forces.

Relative velocity before and after collision have the same magnitude but opposite direction (for elastic collisions):

-Applying the conservation of momentum. The blocks have the same velocity after collision:

#Total Mechanical energy before and after the elastic collision is equal:

Hence, the maxumim energy stored is U=3.3466J, and the velocity=0.333m/s
b. Taking the end collision:
From a above, 
We plug these values in the equation:


Answer:
(i)
, (ii)
, (iii) 
Explanation:
(i)
and
represent the points where particle has a velocity of zero and spring reach maximum deformation, Given the absence of non-conservative force and by the Principle of Energy Conservation, the position where particle is at maximum speed is average of both extreme positions:

(ii) Maximum accelerations is reached at
and
.

(iii) Greatest net forces exerted on the particle are reached at
and
.

To develop this problem it is necessary to apply the concepts related to the Dopler effect.
The equation is defined by

Where
= Approaching velocities
= Receding velocities
c = Speed of sound
v = Emitter speed
And

Therefore using the values given we can find the velocity through,


Assuming the ratio above, we can use any f_h and f_i with the ratio 2.4 to 1


Therefore the cars goes to 145.3m/s
If we neglet air resistance for both objects then both will fall parallely(at same time) because time taken by both objects is independent of mass. there is famous experiment i.e"feather coin experiment" . normally we think that heaver objects falls faster but this is wrong concept. it depends on medium in which objects are moving.
thanku
The answer would be C since metals have electrons that help in heating up the metal