How can an object be moving at a constant velocity but still the sum of the forces is zero?

Question

If the forces equal zero, then dont the forces cancel each other out so therefore the object is not moving?

Answer 1

if the sum of the forces is zero, it only means that the acceleration is zero, which means the velocity won't change...therefore, if the velocity is at, say, 5 m/s, it will remain at 5 m/s as long as the sum of the forces continues to equal zero.

Answer 2

> dont the forces cancel each other out...

Yes

>... so therefore the object is not moving?

Not correct. This was the great insight of Newton. He realized that mere _motion_ does NOT require any net forces. A net force is required only for _acceleration_ (i.e., a _change_ in motion, making the object speed up, or slow down, or change direction).

Answer 3

Chrissy,

- Force=mass x acceleration
- acceleration=change of velocity/change of time
- If the velocity is constant the change in velocity equals zero
- If the change of velocity is zero, acceleration is also zero and Force from the formula above equals zero.

Answer 4

Remember that if an object moves at a constant velocity it probably had an initial point of reference where potential energy was all centered.

When it began to move the potential energy decreases and the kinetic energy increases.

In real media, friction takes apart all this kinetic energy and the object will decrease its velocity (braking it) transforming all the kinetic energy into potential energy again.

So this means that is there is no friction an object can move at a constant velocity without applying any external force.

hope this help you

Answer 5

If an object is currently moving and doesn't have anything slowing down its progress (wind resistance, friction, etc.), it doesn't need any force to perpetuate its motion.

Answer 6

Think of a person running on a treadmill.