I cannot figure out if energy is necc. to overcome inertia. Is there no inertia when there is no friciton?

Question

If mass "resists" change then shouldn't we need to apply extra energy to overcome the resistance? If not, then how would a theoretical mass without inertia be any different than mass WITH inertia. We can't expect that objects would move about and change directions without any force applied to the whatsoever, yet I cannot find anywhere a description of the energy that must be applied just because of the inertia. I have asked questions here before and keep getting answers that address the friction. But I thought that inertia was a property inherent in mass under all conditions. Why would it go away without friction? I investigated "impulse" but that seems different than what I am trying to find.

Answer 1

You are correct. We do have to provide energy to overcome the resistance and get something up to speed. We have to do work on the object. Once the work is done and the object has some speed, we call the energy from the work kinetic energy.

Mass is inertia. Inertia is mass. Saying mass without inertia is like saying what would an elephant be like that isn't a pachyderm? It's nonsense. I suppose you could postulate that the gravitational mass were different than inertial mass. Then you could have one object that accelerates through a vacuum in a g-field faster than another. That we don't see this is evidence that mass is mass is mass.

Answer 2

It sounds like you believe that energy must be applied to overcome inertia, and THEN more energy to get it going. That's not the way it works. You ask, "If mass "resists" change then shouldn't we need to apply extra energy to overcome the resistance?" I ask, "extra" in addition to what? All the work that is done on a body changes its motion. But heavier objects resist that force more than lighter objects and are accelerated by a greater amount: F=ma.

"I cannot find anywhere a description of the energy that must be applied just because of the inertia." ALL the energy applied to get an object moving at a given speed is because of inertia. The kinetic energy of a body is 1/2 m v^2, where m is the inertia. The force that must be applied to achieve a given acceleration is F=ma, where m is the inertia. Mass is inertia. Inertia is mass.

Answer 3

Inertia is a massive object's resistance to change in motion. Friction is a force applied to an object when it comes in contact with another object.

If a hovercraft is levitated above the ground, you would still have to apply force to get it moving. You need energy to overcome inertia.

If that same craft is parked on the ground you'll never move it because now you have to overcome inertia and the friction applied by the ground.

So, you are correct. Inertia is a property inherent in massive objects.

Regarding impulse, that's the delivery of force over a time. Slowly pushing someone's nose with my hand is far less destructive than delivering a quick karate palm strike.

Answer 4

Anything with mass has inertia, inertia is proportional to mass. So even if there is no friction, force is required to move a mass. Inertia is not like static friction -- you don't need an initial force to 'break' it and start the object moving. In a frictionless setting, the slightest force will accelerate a massive object, The well-known equation F=ma is all you need.

Answer 5

Inertia is not a force,it's the property of an object to keep doing what it is doing.
If an object is moving it'll will be moving forever unless a force will stop it or speed it up.
If it's standing still it wont' move until a force will push it.
To find that force,list all the forces affecting the object,(gravity,wind resistance,another object etc.) and a little bit higher amount will be the force necessary to overcame inertia.
If you discount friction,once the object is moving it will go on forever.

Answer 6

you are absolutely correct in saying that nothing will change without being acted upon. Remember, a mass will continue to do its current activity unless a force (energy) is applied to cause it to do otherwise. So, a mass sitting motionless will remain that way unless a force changes that. Also, a mass in motion will remain in motion unless friction (or some other force) causes it to change. You must remember that the motion we're referring to is 'simple' motion; that is, a straight line not under any other influence (circular motion is complex!).

Always remember, the main rule of simple inertia is: a body in motion remains in motion and a body at rest remains at rest, unless acted upon byvan external force.

Answer 7

yes