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Question
Explain difference btw inertia and momentum
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Solution
Momentum: The resistance of an object to a change in its state of motion.
That sounds like a fishy definition of momentum to me. A slightly better definition, at least at your level, is that momentum represents the "amount of motion" an object has. Granted, "amount of motion" is a very vague term, but it stands to reason that if "amount of motion" were to be precisely defined, it would have the following characteristics:
The larger an object, the larger its "amount of motion", all else being equal
The faster an object is moving, the larger its "amount of motion", all else being equal
If two objects have equal "amounts of motion" in opposite directions, the total "amount of motion" of the system of both of them is zero
Momentum is a precisely defined quantity that satisfies these principles. For slow-moving, massive objects, it can be calculated by
p=mv
p=mv
.
A much better definition of momentum comes from the fact that it is conserved, but that may be beyond your level so I'll leave it out. (But do know that the fact that momentum is conserved in many situations is what makes it so useful.)
For inertia, on the other hand, this is quite reasonable:
Inertia: a characteristic of an object that resists changes to its state of motion.
The idea is that objects which are harder to move, or whose motion is harder to change, have more inertia. The precisely defined quantity that satisfies these properties is inertial mass, which you probably know as just "mass". (Or actually, energy, but at your level you can pretend it's just mass.).
That sounds like a fishy definition of momentum to me. A slightly better definition, at least at your level, is that momentum represents the "amount of motion" an object has. Granted, "amount of motion" is a very vague term, but it stands to reason that if "amount of motion" were to be precisely defined, it would have the following characteristics:
The larger an object, the larger its "amount of motion", all else being equal
The faster an object is moving, the larger its "amount of motion", all else being equal
If two objects have equal "amounts of motion" in opposite directions, the total "amount of motion" of the system of both of them is zero
Momentum is a precisely defined quantity that satisfies these principles. For slow-moving, massive objects, it can be calculated by
p=mv
p=mv
.
A much better definition of momentum comes from the fact that it is conserved, but that may be beyond your level so I'll leave it out. (But do know that the fact that momentum is conserved in many situations is what makes it so useful.)
For inertia, on the other hand, this is quite reasonable:
Inertia: a characteristic of an object that resists changes to its state of motion.
The idea is that objects which are harder to move, or whose motion is harder to change, have more inertia. The precisely defined quantity that satisfies these properties is inertial mass, which you probably know as just "mass". (Or actually, energy, but at your level you can pretend it's just mass.).
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