2006-10-31 03:40:59 · 7 answers · asked by goring 6 in Science & Mathematics ➔ Physics
short answer:
They contain kinetic energy. This energy will continue to move the object unless another outside enrgy counters its effect.
2006-10-31 03:55:54 · answer #1 · answered by bc_munkee 5 · 1⤊ 1⤋
A force is needed to accelerate anything. So a force is needed to speed up, slow down or change direction.
In the absence of a resultant force the object just continues at rest or uniform motion in a straight line.
The ancient Greeks didn't spot this as on earth we never have a situation where (eg) a moving object is never subject to friction.
Newton realised that in space there would not necessarily be a resultant force and devised his law.
A space vehicle needs only to accelerate out of orbit and will then continue in a straight line for ever, unless it comes into the gravitational field of a large object or something hits it.
2006-10-31 11:46:35 · answer #2 · answered by hippoterry2005 3 · 0⤊ 0⤋
Because of inertia. Things like to keep doing what they did, if there is no reason to change.
In fact, the real question could be "why SHOULDN'T they move perpetually"; and the reason why it was not picked before was because everything around the Greek philosophers from antiquity that they could observe were subjected to friction, and everything in motion came to a rest eventually. It took quite a man (Newton) to insist otherwise and run against the accepted rule.
2006-10-31 11:47:32 · answer #3 · answered by Vincent G 7 · 0⤊ 0⤋
Objects at rest tend to stay at rest and objects in motion tend to stay in motion.
If no force acts upon an object (disturb it) then it will stay in its current condition. This is seen in outer-space where there is no gravity or friction to act upon objects.
We however live on earth where gravity and friction are constantly acting upon objects and causing moving objects to eventually stop.
So, I guess to answer your question - energy is neither created or destroyed and so a moving object has a definite amount of energy and unless that energy is used or converted to another form, the object will continue to move perpetually.
2006-10-31 11:52:43 · answer #4 · answered by Schlump 3 · 1⤊ 0⤋
Because of its inertia. Every object has inertia.
Objects at rest stay at rest, objects accelerating continue to accelerate...unless of course a force acts upon it.
If undisturbed then there is no force acting on it and it will continue whatever it was previously doing.
2006-10-31 11:57:45 · answer #5 · answered by wildbutterflychick 2 · 0⤊ 0⤋
An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
The behavior of all objects can be described by saying that objects tend to "keep on doing what they're doing" (unless acted upon by an unbalanced force). If at rest, they will continue in this same state of rest. If in motion with an eastward velocity of 5 m/s, they will continue in this same state of motion (5 m/s, East). If in motion with a leftward velocity of 2 m/s, they will continue in this same state of motion (2 m/s, left). The state of motion of an object is maintained as long as the object is not acted upon by an unbalanced force. All objects resist changes in their state of motion - they tend to "keep on doing what they're doing."
2006-10-31 11:48:45 · answer #6 · answered by djessellis 4 · 0⤊ 0⤋
Because if things happened randomly and speeds, directions, energies, etc. changed,. it would violate the laws of conservation of energy and thermodynamics.
Doug
2006-10-31 11:45:54 · answer #7 · answered by doug_donaghue 7 · 0⤊ 0⤋