Does a conservative force always = a change in kinetic energy?

Question

I'm going to major in physics next yr in university. so I've been thinking about work and energy and trying to really understand it ..but now I'm confusing the hell out of myself lol with conservative and non conservative forces and work,etc

For ex. I was thinking about gravity technically doing negative work on an object when you push it up and then the applied force doing positive ..and then when you let it go ..gravity does positive work and ..yea..confused..

then I was thinking about spring forces, electric forces etc ..friction

Can someone just help me look at these problems in a unified way .should I always just add the Potential and kinetic energy + work = Etf or Should I just add the potential energy + work done by a conservative force + work done by applied force. ..
um ..........


HELP!!!!!!!!

Answer 1

No. A force is never equal to an energy.

Answer 2

Your statement that
‘. I was thinking about gravity technically doing negative work on an object when you push it up and then the applied force doing positive. And then when you let it go down, .gravity does positive work’.

IS CORRECT.

Gravity doing Negative work implies THE OBJECT’S ENERGY IS DECREASING.

Consider an object of mass at rest on the horizontal ground. Applying a force we make it move in the horizontal direction and the objects attains a speed v. We remove the force.

The work done by the force is stored as K.E in the object.

The gravitational force does no work on this object.

By providing an arc of circular path, we change the direction of motion of the object exactly vertically up to the ground. (Note that no work or energy is needed for this).
The object which had a stored energy (K.E) is loosing its speed as it goes up and up.

The motion of the object is against gravitational force; work is negative; the object’s energy is decreasing.

By providing an arc of circular path, we change the direction of motion of the object exactly vertically down to the ground.

The motion of the object is along gravitational force; work is positive ; the object’s energy is increasing, its speed increases.


Coming to the second part,

Sum of the P.E and K.E is a constant.

DO NOT INCLUDE THE WORK TERM HERE IN THE CASE OF CONSERVATIVE FORCES.

When P.E is lost it is manifested as K.E and vice versa.

If any external work or energy is added to that object, other than by gravity, use the principle of conservation of energy which is valid in any system.