When weight acting downwards is equal to air resistance acting upwards why is the object falling???
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I don’t get that if weight is the only force acting downwards (xN) and air resistance is exactly equal (xN) then there is 0 resultant force so the object should go anywhere????????
I don’t get that if weight is the only force acting downwards (xN) and air resistance is exactly equal (xN) then there is 0 resultant force so the object should go anywhere????????
I think a lot of answers here are just accepting a flawed premise…
While gravity may not be a force in the same way as other proper “forces” in physics… It’s close enough… It acts on objects more or less directly… And only as a product of the masses of and distance between the objects… To oversimplify it’s fine to imagine it being a “pull” large objects have on much much smaller ones
Air resistance however isn’t a for in the same way… It’s just air having mass and taking time to get out of the way… If you drop a tennis ball down through a room full of ping pong balls… It’s going to take you longer because of “ping pong ball resistance” for basically the same reason as a feather falls slowly due to air resistance… But you wouldn’t typically imagine ping pong balls are pushing the tennis ball up (except in the somewhat less intuitive newton’s-third-law sense that when you push a car the car pushes you back)…
That’s to say… Gravity keeps “pulling” you… Air resistance stops when you stop… And increases when you accelerate, and works in every direction… So for anything with a higher density than air there is a speed at which it causes so little air resistance that gravity wins… If gravity doesn’t win it slows down, which reduces the air resistance… If there is no speed at which it can continue falling that means the object is equal or lower density than the surrounding air and it “floats”
Tldr: the premise is flawed… air resistance isn’t a force in the same way as gravity… It scales down with velocity of the item until it falls unless the item is as dense or less so than air
edit: in still air. if you mean the air is moving up to counter gravity, like one of those vertical wind tunnels doe mock-skydiving… in which case that’s not very much different than throwing a stream of ping pong balls up at the object so that you’re pushing it up as fast as it’s being pulled down in which case it hovers… that’s functionally equivalent to increasing it’s speed in the air, which increases the resistance of the air until it matches the downward pull
Forces act on acceleration, not speed. If the resulting force is 0, that means the acceleration is also 0 but it says nothing about the speed of the object. All you can know is that whatever speed it’s at, is constant. For a falling object being affected by gravity and drag, that speed is the terminal velocity
Forces act on acceleration, not speed. If the resulting force is 0, that means the acceleration is also 0 but it says nothing about the speed of the object. All you can know is that whatever speed it’s at, is constant. For a falling object being affected by gravity and drag, that speed is the terminal velocity
if net forces on an object is zero, then the object will continue at constant speed as before.
if the previous speed was zero, then it will stay zero. if the previous speed was falling at 1m/s, then it will continue to do so.
this is how terminal velocity occurs.
I think a lot of answers here are just accepting a flawed premise…
While gravity may not be a force in the same way as other proper “forces” in physics… It’s close enough… It acts on objects more or less directly… And only as a product of the masses of and distance between the objects… To oversimplify it’s fine to imagine it being a “pull” large objects have on much much smaller ones
Air resistance however isn’t a for in the same way… It’s just air having mass and taking time to get out of the way… If you drop a tennis ball down through a room full of ping pong balls… It’s going to take you longer because of “ping pong ball resistance” for basically the same reason as a feather falls slowly due to air resistance… But you wouldn’t typically imagine ping pong balls are pushing the tennis ball up (except in the somewhat less intuitive newton’s-third-law sense that when you push a car the car pushes you back)…
That’s to say… Gravity keeps “pulling” you… Air resistance stops when you stop… And increases when you accelerate, and works in every direction… So for anything with a higher density than air there is a speed at which it causes so little air resistance that gravity wins… If gravity doesn’t win it slows down, which reduces the air resistance… If there is no speed at which it can continue falling that means the object is equal or lower density than the surrounding air and it “floats”
Tldr: the premise is flawed… air resistance isn’t a force in the same way as gravity… It scales down with velocity of the item until it falls unless the item is as dense or less so than air
edit: in still air. if you mean the air is moving up to counter gravity, like one of those vertical wind tunnels doe mock-skydiving… in which case that’s not very much different than throwing a stream of ping pong balls up at the object so that you’re pushing it up as fast as it’s being pulled down in which case it hovers… that’s functionally equivalent to increasing it’s speed in the air, which increases the resistance of the air until it matches the downward pull
I think a lot of answers here are just accepting a flawed premise…
While gravity may not be a force in the same way as other proper “forces” in physics… It’s close enough… It acts on objects more or less directly… And only as a product of the masses of and distance between the objects… To oversimplify it’s fine to imagine it being a “pull” large objects have on much much smaller ones
Air resistance however isn’t a for in the same way… It’s just air having mass and taking time to get out of the way… If you drop a tennis ball down through a room full of ping pong balls… It’s going to take you longer because of “ping pong ball resistance” for basically the same reason as a feather falls slowly due to air resistance… But you wouldn’t typically imagine ping pong balls are pushing the tennis ball up (except in the somewhat less intuitive newton’s-third-law sense that when you push a car the car pushes you back)…
That’s to say… Gravity keeps “pulling” you… Air resistance stops when you stop… And increases when you accelerate, and works in every direction… So for anything with a higher density than air there is a speed at which it causes so little air resistance that gravity wins… If gravity doesn’t win it slows down, which reduces the air resistance… If there is no speed at which it can continue falling that means the object is equal or lower density than the surrounding air and it “floats”
Tldr: the premise is flawed… air resistance isn’t a force in the same way as gravity… It scales down with velocity of the item until it falls unless the item is as dense or less so than air
edit: in still air. if you mean the air is moving up to counter gravity, like one of those vertical wind tunnels doe mock-skydiving… in which case that’s not very much different than throwing a stream of ping pong balls up at the object so that you’re pushing it up as fast as it’s being pulled down in which case it hovers… that’s functionally equivalent to increasing it’s speed in the air, which increases the resistance of the air until it matches the downward pull
Newtons Law postulates that an object at rest *or at rest* will continue to remain at rest or uniform motion unless acted upon by an exterior force.
What this means is that if there is no (net) force acting on an object, then it’s speed won’t change, not that it won’t move.
If it’s already moving, then it’s speed will stay constant, and if it’s not moving it will equally stay constant (in this case at zero)
If you are driving a car, and you stop accelerating or braking, why do you keep on moving forward. Shouldn’t you just come to a sudden and complete stop??
(I am providing an example where your logic in incorrect, I am not advocating this position)
Or, more correctly. If you are holding the gas petal down slightly (constant gravity), and the air resistance and tire resistance has balanced out the cars acceleration, you will keep going to same speed.
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