# Force with regard to 0 acceleration

• joel amos
In summary: They all involve the application of a force to produce an acceleration.In summary, Ball A travels at a constant velocity until it collides with Ball B, at which point it exerts a force on Ball B and is accelerated in the opposite direction. This does not contradict the fact that at 0 acceleration, Ball A cannot produce a force according to F = ma. Both statements are true and describe different situations.
joel amos
Premise: Ball A is accelerated on a level, frictionless plane until it reaches a velocity of 5 m/s. Ball A travels at 0 acceleration until it collides with Ball B.

Statements:
1. According to F = ma , Ball A cannot produce a force at 0 acceleration.
2. Upon collision, Ball A applies a force on Ball B.

From what I've learned, both of the statements are true. However, they clearly contradict each other. What's the cause of my confusion?

Once the ball A hits the ball B, its velocity will change and hence it will have acceleration and therefore apply force to B.

joel amos said:
1. According to F = ma , Ball A cannot produce a force at 0 acceleration.
Just because a given object is not itself accelerating doesn't mean it can't exert a force on something else. If I place a book on top of a table then it isn't accelerating but it exerts a downward force on the table. Similarly let's say we have some particle A traveling with some constant velocity towards some particle B, which is also traveling at some constant velocity towards A. When A collides with B, A exerts some force on B and by Newton's 3rd law B will exert an equal and opposite force on A.

hokhani said:
Once the ball A hits the ball B, its velocity will change and hence it will have acceleration and therefore apply force to B.

But wouldn't the acceleration of Ball A be negative upon impact, causing the force applied to be negative. If the force is negative, wouldn't that mean that Ball B moves in the opposite direction?

According to the third Newton's law, it doesn't matter to say A applied force to B or vice versa.

joel amos said:
Statements:
1. According to F = ma , Ball A cannot produce a force at 0 acceleration.
Newton's 2nd law tells you that 0 acceleration means zero net force. During its travel at constant velocity, the net force on the ball must be zero.

2. Upon collision, Ball A applies a force on Ball B.
And Ball B applies an equal and opposite force on Ball A. Once the collision happens, it's no longer true that there is 0 net force on Ball A or that its acceleration is zero.

From what I've learned, both of the statements are true. However, they clearly contradict each other. What's the cause of my confusion?
No contradiction at all. They describe different situations.

joel amos said:
But wouldn't the acceleration of Ball A be negative upon impact, causing the force applied to be negative. If the force is negative, wouldn't that mean that Ball B moves in the opposite direction?
If you call the original direction of motion of Ball A the positive direction, then Ball B will exert a negative force on Ball A. Which means that Ball A will be accelerated in the negative direction (slowing it down).

And Ball A exerts a positive force on Ball B, giving Ball B a positive acceleration.

Doc Al said:
If you call the original direction of motion of Ball A the positive direction, then Ball B will exert a negative force on Ball A. Which means that Ball A will be accelerated in the negative direction (slowing it down).

And Ball A exerts a positive force on Ball B, giving Ball B a positive acceleration.

Thanks!

There really is no distinction between "acceleration" and "deceleration" from an F=ma standpoint. Negative and positive values only mean that the direction is different, but it's still "acceleration". Pressing on the gas pedal, stepping on the brake pedal, or going around the Earth in a satellite are all the same from an F=ma standpoint.

## 1. What is force with regard to 0 acceleration?

Force with regard to 0 acceleration refers to the amount of push or pull applied to an object when there is no change in its velocity or speed. This means that the object is either at rest or moving at a constant speed.

## 2. How is force related to acceleration?

According to Newton's second law of motion, force is directly proportional to acceleration. This means that the greater the force applied to an object, the greater its acceleration will be. Similarly, if there is no force acting on an object, it will have 0 acceleration.

## 3. Can an object have a force acting on it but still have 0 acceleration?

Yes, an object can have a force acting on it but still have 0 acceleration if the force is cancelled out by an equal and opposite force. This can happen when an object is in equilibrium, meaning that the net force acting on it is 0.

## 4. How is force measured when there is 0 acceleration?

When there is 0 acceleration, the force acting on an object can be measured using a spring scale or a force sensor. These devices measure the amount of force applied to an object in units of newtons (N).

## 5. What are some examples of forces acting on objects with 0 acceleration?

Examples of forces acting on objects with 0 acceleration include a book sitting on a table (with the force of gravity being cancelled out by the normal force of the table), a car moving at a constant speed on a flat road (with the force of the engine being cancelled out by the resistance forces), and an object in outer space (with no external forces acting on it).

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