Answer:
21.8 m/s
Explanation:
At the top of the hill (crest), there are two forces acting on the motorcycle:
- The reaction force of the road, N (upward)
- The force of gravity, mg (downward)
Since the motorcycle is moving by circular motion, the resultant of these forces will give the centripetal force, so:

where the direction of the weight (mg) is equal to that of the centripetal force, and where
m is the mass of the cycle
g = 9.8 m/s^2 is the acceleration of gravity
v is the speed
r = 48.6 is the radius of the hill
The cycle loses contact with the road when the reaction force becomes zero:
N = 0
Substituting into the equation, we therefore find the maximum speed that is allowed for the cycle before losing constact:

Answer:
a. the force between them quadruples
Explanation:
The electrostatic force between two charges is given by

where
k is the Coulomb's constant
q1 and q2 are the two charges
r is the separation between the two charges
In this problem, the charges on both objects are doubled, so

While the distance does not change, so the new force will be

so, the force will quadruple.
Answer: Option (a) is the correct answer.
Explanation:
Resources which are created by human beings are known as man-made resources.
For example, glass, rayon, nylon etc are all man-made resources.
Whereas resources which are naturally created are known as natural resources.
For example, wind, air, water etc are all natural resources.
Thus, we can conclude that out of the given options time is not a natural resource.
The Photosphere is the right answer