Answer:
8.56 m/s2
Explanation:
Using law of energy conservation while taking into account of the rotational and translation kinetic energy, when the solid cylinder rolls down the incline we have the potential energy converted to kinetic energy:


where m is the mass,
is the moments of inertia of the solid cylinder
is the angular speed of the cylinder



So if you plot a liner chart of h vs
and get a slope of 6.42 then that means 3/(4g) = 6.42 so 
The gravitational acceleration on this planet is 8.56 m/s2
Answer:
A) and B) are correct.
Explanation:
If the object is at rest, it means that no net force is exerted on it.
As the object experiences a downward gravitational force from Earth, in order to be at rest, it must experience an upward force with the same magnitude as the gravitational force on the object.
This force is supplied by the normal force, which can adopt any value in order to meet the condition imposed by Newton´s 2nd Law, and is always perpendicular to the surface on which the object is placed (in this case, the ground).
At a molecular level, this normal force is supplied by the bonded molecules of the ground that behave like small springs being compressed by the molecules of the object, exerting an upward restoring force upward on them.
So, the statements A) and B) are true.
It is a seismograph that would be most useful.
Answer:

Explanation:
The system is modelled after the Principle of Energy Conservation and the Work-Energy Theorem:



An object can be at rest and still be in motion because the earth is always in motion.