The Coulomb force between two or more charged bodies is the force between them due to Coulomb's law. If the particles are both positively or negatively charged, the force is repulsive; if they are of opposite charge, it is attractive. ... Like the gravitational force, the Coulomb force is an inverse square law.
Before the engines fail
, the rocket's horizontal and vertical position in the air are


and its velocity vector has components


After
, its position is


and the rocket's velocity vector has horizontal and vertical components


After the engine failure
, the rocket is in freefall and its position is given by


and its velocity vector's components are


where we take
.
a. The maximum altitude occurs at the point during which
:

At this point, the rocket has an altitude of

b. The rocket will eventually fall to the ground at some point after its engines fail. We solve
for
, then add 3 seconds to this time:

So the rocket stays in the air for a total of
.
c. After the engine failure, the rocket traveled for about 34.6 seconds, so we evalute
for this time
:

Answer:
D. 1.8 × 102 newtons radially inward
Explanation:
The magnitude of the centripetal force is given by:

where
m is the mass of the object
v is the tangential speed
r is the radius of the circular trajector
In this problem, we have m = 4.0 kg, v = 6.0 m/s and r = 0.80 m, therefore substituting into the equation we get

The centripetal force is the force that keeps the object in a circular trajectory, so it is a force that is always directed inward (towards the centre of the circular path) and radially. Therefore, the correct answer is
D. 1.8 × 102 newtons radially inward