Answer:
a.
b.
Explanation:
We are given that




a.We have to find the angle


b. We have to find the speed 
According to law of conservation of momentum



Answer:

Explanation:
The interaction of the piece of copper and water means that the first one need to transfer heat in order to reach a thermal equilibrium with water. Then:

After a quick substitution, the expanded expression is:



The final temperature of the system is:

Answer:
(1) Resonance
Explanation:
Resonance is the process whereby a system is set into vibration due to the vibration of a nearby system with larger amplitude. The frequency at which this vibration takes place is called the resonant frequency.
It is a phenomenon of amplification that occurs when the frequency of a periodically applied force is in harmonic proportion to the natural frequency of the system on which it acts.
A kilogram is a unit of weight. So a kilogram of bricks would weigh the same as a kilogram of feathers despite if its in water or air since weight is determined by gravity in relation to mass and not what substance the object is in.