Mantle plumes are regions of warm, up-welling covering. A hot spot occurs over the plume. It generates the magma that emanates by the unbreakable plates of the lithosphere and provides active volcanoes at the surface of the earth. In other words, the hot spots are found in the mantle where cliffs melt to form magma. It creates a volcanic region a few hundred kilometers across.
The Net Force of an object should be the difference between the forces applied to the object if the object is not in equilibrium. This object is not in equilibrium so therefore by finding the difference between the forces, you will find your answer. 20 N - 7 N = 13 N.
When at the bottom of the dip, the only force that keeps the car in the circular trajectory, is the centripetal force.
This force is not a new force, is just the net force aiming to the center of the circle.
In this case, is just the difference between the normal force (always perpendicular to the surface, pointing upward) and the force that gravity exerts on the car (which is known as the weight), pointing downward.
So, we can write the following expression:
It can be showed that the centripetal force is related to the speed by the following expression:
The normal force, it is called the apparent weight, because it would be the weight as measured by a scale.
Replacing (2) in (1), and solving for Fn, we get:
Now, we need to find the value of v that makes Fn, exactly 15% more than the weight m*g, so we can write the following equation:
Replacing Fg by its value, simplifying, and solving for v, we get: