i just dont get this?

Question

why is there a equal force that goes up and down on a stationary object? and also why do they calculate acceleration in m/s^2

Answer 1

for an object to stay still the force acting on each side must be the same, if gravity is pulling down on it, the the ground has to exert as much force or else the object woudl sink into the ground, and acceleration is in m/s^2 because if a car is moving 60 m a second its not gaining or loosing speed, but if its traveling 60 m/s/s its gaining speed, so the frist second it woudl be going 60m/s, the second second woudl be moving 120m/s the third woudl be 180m/s and so on

Answer 2

Because if the forces were unequal the object would be accelerating. If the table that a book was setting on didn't 'push' upwards with the exact same force as the book pushed 'downwards', then the book would move.

If you pick the book up off of the table, you must exert *more* force against the book (in the upward direction) than the table does. And, when you have the book at the level you want, you exert exactly the same amount of force ('push') against the book as the table did.

Acceleration is in m/s² because it's the rate of change of velocity. Velocity is measured in m/s and so m/s divided by seconds is (m/s)/s => (m/s)/(s/1) To divide fractions you invert and multiply so (m/s)*(1/s) = m/s². It might make more sense if you said, "Meters per second per second." while you're getting used to the concept.

Hope that helps.


Doug

Answer 3

It is really about balance relative to something else, since stationary is relative to some observer. But if something is sitting on a table, then gravity is pulling it down, and the forces in the table (the forces from the molecules in the table) keep the object from merging into the table. So it is not moving up, or down, and is "stationary".

Answer 4

Think of it this way: If you were sitting in a chair and not moving, the chair is providing enough 'resistance' to keep you from falling on the floor. The air around you is exerting equal force on all points around you, therefore it doesn't push you one way or the other.

If a bomb blew up under your chair, the 'force' of the blast would throw you in the opposite direction of its epicenter of 'energy'. The energy has to dissipate and the part that hits you uses your mass as a vehicle because you just happened to be in the way. Now that your body is in motion you have 'inertia' which will keep you in motion until the energy has been expended.
If you are in space you may keep going forever because there is little or no resistance. On earth your flight would be limited due to gravity and external resistances (atmospheric density, tree limbs, the ceiling, etc).

Answer 5

Because when the object is stationary, the gravity is exerting a force equivalent to the positive force holding the object. m/s^2 meaning you velocity per a second, which should read meters per a second per a second, because velocity is measured in m/s