Answer : The static friction depends on two factors
1. Roughness of the surface
2. Force
Explanation : Friction occur when surface is not smooth.
The formula of friction is

Static friction depends on the roughness of the surface and force which is trying to push to object along the surface.
Static friction is caused by the attraction between two surfaces that are in contact. when the surface will rough and the object will heavier then the force will be larger.
If each mL has 30 grams of the substance in it, then 60 mL have 1800 grams of mass in them. the weight of 1,800 grams of mass on Earth is (1.8 kg) x (9.8 m/s^2) = 17.6 newtons.
It is C. A description goes into the details about something, and an explanation is a statement that clarifies something, generally a question.
Explanation:
Seismic refraction is the bending of the seismic waves as they pass geological layers of the earth due to different densities. This is especially true for Primary waves because they can pass through all the layers of the earth both liquid and solid.
Seismic reflectivity is the bouncing back of seismic waves at a boundary of geological layers due to different densities or subsurface formation. This is especially true for secondary waves that are unable to pass through liquid layers of the earth like the outer core and mantle. When they reach the boundary of these layers they bounce back towards the earth's surface.
These properties of P and S waves are used to ‘auscultate’ the epicenter of an earthquake by triangulation.
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Answer:
12 units
Explanation:
Original F = C q1q2/r^2 now change the parameters
New F = C 1/3 q1 2 q2 / (2r)^2
= 2/12 C q1q2/r^2 <=======the new force is 1/6 of original
1/6 * 72 = 12 units