Newton's first law states that, in the absence of any forces, an object in motion will remain in motion forever or eventually come to rest.
Consider two objects with the same mass. If one object is moving and the other object is not, which object has the most inertia? the object which is moving the object which is not moving Both objects have the same inertia.
If I push on an object which is at rest (like the wall), then the force exerted by my hand on the object will be equal to the force exerted by the object on my hand. However, if I push on an object, causing it to accelerate, then the force exerted by my hand on the object will be greater than, less than, or still equal to the force exerted by the object on my hand.
Ralph asked me a question the other day. Suppose he's driving his car and a bug hits his windshield. The bug is totally smashed, but the windshield is unaffected. Doesn't this mean that the force exerted by the windshield on the bug is greater than the force exerted by the bug on the windshield? How would you answer his question? Be sure to explain why. Newton's third law guarantees that the two forces are equal (and opposite). It doesn't take much force to smash a bug. The same amount of force that smashes a bug does not have much affect on the windshield.