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 
Answer:
The acidic or the basic nature of a substance can be determined using a pH indicator. If the pH indicator , shows a pH value less than 7 , the substance is acidic. Lower the pH , high is the acidic nature.
Explanation:
The block on the action of two forces, the Force of Friction and the Tangential Weight. Using the Newton's Secound Law, we have:
Using the Velocity Hourly Equation, we get:
Uniting the equations:
Entering the unknowns:
Obs: Approximate results
If you notice any mistake in my english, please let me know, because i am not native.
