Answer:
Velocity will be 
Explanation:
We have given mass of alpha particle m = 4 u 
Charge on alpha particle 
Charge on thorium particle 
Diameter is given as d = 15 fm
So radius 
Potential energy is given by 
From energy conservation 


To develop this problem we will apply Newton's laws regarding gravitational forces, both in space and on earth. From finding this relationship, leaving the variable of the dust mass open, we will find the relationship of the forces between the two surfaces. Our values are,



Distance between the center of lead sphere to dust particle



Gravitational force of the sphere on the dust particle:



Weight of the dust particle


Ratio of F and W:


Therefore the ratio is 
The power is calculated using the following rule:
Power = voltage * current
We are given that:
power = 10 watts
voltage = 3 volts
Substitute with the givens in the above equation to get the value of the current as follows:
P = V*I
10 = 3*I
current (I) = 10/3 amperes
Answer: Heat transfer due to emission of electromagnetic waves is known as thermal radiation.
Explanation: Heat transfer through radiation takes place in form of electromagnetic waves mainly in the infrared region. Radiation emitted by a body is a consequence of thermal agitation of its composing molecules.
Answer:
PO(1) = PO(0) / 2 1 refers to 1 half life of PO(0)
PO(2) = PO(1) / 2 = P(0) / 4 amount of PO left after 2 half-lives
PO(3) = PO(2) / 2 = PO(0) / 8 amount of PO left after 3 half-lives
414 da / 138 da = 3 3 half-lives pass in 414 da
PO(0) = 8 PO(3) = 8 * 1.45E-4 g = 1.16E-3 g = .00116 g after 414 days