Answer:

Explanation:
a) Fundamental frequency
A harmonic is an integral multiple of the fundamental frequency.


b) Wave speed
(i) Calculate the wavelength
In a fundamental vibration, the length of the string is half the wavelength.

(b) Calculate the speed
s



Using the Fundamental Equation of Wave, we have:
Letter B
Answer:
C. both forces have the same magnitude
Explanation:
Here the action force is equal to the reaction force in accordance with the Newton's third law of motion.
Also when we apply the conservation of momentum so that the momentum bullet and the momentum of the gun are equal and according to the second law of motion by Newton, we have force equal to the rate of change in momentum.
We have the equation for momentum as:

Newton's second law is Mathematically given as:

Momentum is constant and the reaction time is equal, so the force exerted will also be equal.
Answer:
Time taken by A and B is 1.2 hr.
Explanation:
Given that
Time taken by tank when all(A+B+C) are open = 1 hr
Time taken by tank when A+C are open = 1.5 hr
Time taken by tank when B+C are open = 2 hr
If we treat as filling of tank is a work then
Work = time x rate
Lets take work is 1 unit
1 = 1(1/a+1/b+1/c) ---------1
1 = 1.5(1/a+1/c) ----------2
1 = 2(1/b+1/c) --------3
From equation 1 and 3
1=1(1/a+1/2)
a=2
Form equation 2
1 = 1.5(1/2+1/c)
c=6
From equation 3
1 = 2(1/b+1/6)
b=3
So time taken by
A is alone to fill tank is 2 hr
B is alone to fill tank is 3 hr
C is alone to fill tank is 6 hr
So 
Time taken by A and B is 1.2 hr.
Answer:
4. total energy
Explanation:
According to Bernoulli's principle at any two points along a streamline flow The total energy that is sum of pressure energy , Kinetic energy and potential energy of the liquid all taken in per unit volume remains constant. Therefore,
for ideal fluid flows through a pipe of variable cross section without any friction. The fluid completely fills the pipe. At any given point in the pipe, the fluid has a constant Total Energy.