Explanation:
a) Density is the amount of mass in a specific amount of volume
b) Some substances are less dense than water so will float and vice versa
c) The wooden plank has less density than water due to having larger volume and vice versa with the wooden block since volume and density are inversely proportional
II) (a) They are all metals
(b) water -> Compound
oxygen -> Element
Gold-> Element
Salt-> Compound
Answer: 
Explanation:
Given
Radioactive material is found to decrease 40% of its original value in 
Sample at any time is given by

where, 
Put values

Taking natural logarithm both side

Based on the physics principle of conservation of energy, this radiation budget represents the accounting of the balance between incoming radiation, which is almost entirely solar radiation, and outgoing radiation, which is partly reflected solar radiation and partly radiation emitted from the Earth system, including the atmosphere.
Answer:

Explanation:
The intensity of an electromagnetic wave can be expressed in terms of the magnetic field using the next relationship:
(1)
- c is the speed of light (3*10⁸ m/s)
- μ₀ is the permeability of free space (in vacuum ) (1.26*10⁻⁶ N/A²)
- B₀ is the magnetic field


Now, let's define the relationship between power (P) and average intensity (I).

- P is the power
- A is the area crossed
So we can calculate the power.

Finally, energy is the product of P times time, so:

I hope it helps you!
100. A centimeter is a 100th of a meter.