If every force has an equal and opposite reaction, why is it that dents form when you drop a heavy object onto the ground? Does this mean that the downward force exerted by the object is momentarily greater than the upward force exerted by the ground?
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Not at all. It only means that the ground is softer than the item dropped so the ground bends rather than the object.
The forces are identical but one surface is weaker than the other.
To test this try a softer item. For example a pillow. Drop it and see which one bends more on contact.
The ground or the pillow.
And to whomsoever gave a thumbs down to this. Best hit the text books.
EVERY action has an equal and opposite reaction.
Always. In every case.
The forces are identical but one surface is weaker than the other.
To test this try a softer item. For example a pillow. Drop it and see which one bends more on contact.
The ground or the pillow.
And to whomsoever gave a thumbs down to this. Best hit the text books.
EVERY action has an equal and opposite reaction.
Always. In every case.
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Yes, you've got it. The object will not come to rest until the forces are equal.
There's also the question of the conservation of momentum. Hitting a 'non-elastic' substance like the ground, the momentum of the object is passed onto the particles of dirt and the energy is dissipated as heat. If the object was dropped onto a hard surface (like a steel plate), then most of the momentum will be conserved in the object, causing it to bounce. However, at the instant at which it changed direction, its motion was stopped. This is the point at which the upward force of the steel plate equalled the downward force of the object.
There's also the question of the conservation of momentum. Hitting a 'non-elastic' substance like the ground, the momentum of the object is passed onto the particles of dirt and the energy is dissipated as heat. If the object was dropped onto a hard surface (like a steel plate), then most of the momentum will be conserved in the object, causing it to bounce. However, at the instant at which it changed direction, its motion was stopped. This is the point at which the upward force of the steel plate equalled the downward force of the object.
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Andrew Smith's answer is correct, even though someone gave it a 'thumb's down' (but I gave it a thumb's up!)
The magnitude of the force of the object on the ground is exactly equal to the magnitude of the force of the ground on the object.
These 2 forces aren't constant until the object has stopped decelerating. The forces are zero at the moment of contact, grow to a maximum, and then reduce to a steady value (numerically equal to the weight). Quite complicated - but the forces are always equal magnitudes (and opposite direction) at any moment of time.
It is the nature of the different materials that causes one object to deform more than the other other.
The magnitude of the force of the object on the ground is exactly equal to the magnitude of the force of the ground on the object.
These 2 forces aren't constant until the object has stopped decelerating. The forces are zero at the moment of contact, grow to a maximum, and then reduce to a steady value (numerically equal to the weight). Quite complicated - but the forces are always equal magnitudes (and opposite direction) at any moment of time.
It is the nature of the different materials that causes one object to deform more than the other other.
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I may be getting ahead of where you are, but your question involves Momentum and/or Energy. Because the object is falling and has a velocity at impact with the ground, the ground must exert an IMPULSE or do WORK (Energy) to stop the object. Either way you analyse it, you get a dent.
Momentum = Impulse
mass * velocity = force * time (Nothing happens in 0 time, how long it took for the dent to form)
Energy = Work
0.5* mass * velocity^2 = force * distance (How deep the dent is)
Momentum = Impulse
mass * velocity = force * time (Nothing happens in 0 time, how long it took for the dent to form)
Energy = Work
0.5* mass * velocity^2 = force * distance (How deep the dent is)