Explanation:
The speed of a wave is given by :
......(1)
(i) Here, the wavelength of a sound wave in air reduces by a factor of 3. Equation (1) becomes :

Wavelength and frequency are inversely proportional to each other. So, if wavelength of a sound wave in air reduces by a factor of 3, then the frequency will increases by a factor of 3.
(ii) It remains the same.
Answer:
F_n = 5.65E-11 N
d = 1.20682E-31 m
Explanation:
F = 3.8E-09 N
where
m = Mass of electron = 9.109E−31 kilograms
G = Gravitational constant = 6.67E-11 m³/kgs²
x = Distance between them

For 

Dividing the above equations we get

F_n = 5.65E-11 N

d = 1.20682E-31 m
Answer:
Efficiency = 80%
Explanation:
Given the following data;
Work output = 240 N
Work Input = 300 N
To find the mechanical efficiency of a machine;
Substituting into the equation, we have;

Efficiency = 80%
Therefore, the mechanical efficiency of the machine is 80 percent.
The colors of light emitted from heated atoms had very specific energies.
Answer:
90°
Explanation:
The angle will be 90° when momentum for a system can be conserved in one direction while not being conserved in another.
The example can be
If we apply force on an object horizontally in west direction, then as in other direction south or north we cannot apply the principal of momentum conservation.