Question

Does the kinetic energy of an object depend on its gravitational potential energy? use evidence to explain your answer.

Answer 1

Short answer: No

Step-by-step explanation:

Long answer: Kinetic energy is the amount of energy in a moving object. Gravitational potential energy is the energy in an object because of the object's position in the gravitational field.

Imagine a car travelling along a road. There is a wall at one end of the road and car collides with this wall. The energy released when the car collides with the wall is the kinetic energy of the moving car. To have kinetic energy an object must have velocity. The equation for the kinetic energy of a moving object is

K.E =
`(1)/(2) mv^(2)` , where m is the mass of the object and v is velocity. So, if velocity is zero (i.e. the object isn't moving), K.E = 0.

Now, imagine a car falling from a plane which is flying at a height of 300 metres from the ground. The energy the car possesses at a height of 300m is its gravitational potential energy. This is the energy which causes the falling car to move toward the ground in the first place.

You might think that as the car moves towards the ground, it has velocity since it's moving. Well, yes; the car does have kinetic energy, but only when it starts moving; the car does not have any kinetic energy when it's on the cargo hold of the plane. It is the gravitational potential energy of the car which causes an increase in kinetic energy. The equation for gravitational potential energy is:

`G.P.E = mgh` , where m= mass of the object, g is the gravitational field strength (i.e 10N/kg) and h is the height of the object from the ground. So, imagine if the car parked on the ground, its gravitational potential energy would be zero, and if gravitational potential energy is zero, then there will be no force to cause the car to start moving and gain kinetic energy.

In this sense, you might say that the kinetic energy of the object does depend on its gravitational potential energy, but remember, in the first example, the car was not moving downwards; it was moving horizontally. So gravitational potential energy only affects kinetic energy downwards, but kinetic energy can be in any direction.

And hence, gravitational potential energy does not affect kinetic energy.