Answer:
a. 8p
Explanation:
We are given that
Radius of hollow sphere , R1=R
Density of hollow sphere=
After compress
Radius of hollow sphere, R2=R/2
We have to find density of the compressed sphere.
We know that


Therefore,
Volume of sphere=
Using the formula



Hence, the density of the compressed sphere=
Option a is correct.
Answer:
Mechanical
Explanation:
The tank is at rest. And energy of any substance at rest is known as potential energy.
Now, in forms of energy, potential energy is a type of mechanical energy.
Thus, the correct option is mechanical Energy.
A small 20-kg canoe is floating downriver at a speed of 2 m/s. 40 J is the canoe’s kinetic energy.
Answer: Option A
<u>Explanation:</u>
The given canoe has the mass and is being given to move at a speed. Therefore the kinetic energy of the canoe can be calculated using the following method,
Given that mass of the canoe = 20 kg and its speed =1 m/s
As we know that the Kinetic energy has the formula,

Therefore, substituting the value into the equation, we get,
= 40 J
V (speed) = F (frequency) x Wavelength
If we rearrange the formula, making frequency the subject;
F (frequency) = Speed ÷ Wavelength
F = 300,000 m\s x 4.5 e -10m
F = 0.08810409956 Hz