Net Force Questions: Answers to Help Solve Problems

[kye6338]

Hi,
I was hoping someone could help me with some general net force questions that will help me answer some of my problems. For example, if a net force acts on an object, does the object's speed and/or velocity change? Furthermore, is the net force that acts on an object which remains at rest equal to zero?

Going off of the velocity question from above, will a car, for example, initially moving at a constant velocity slow down unless a small net force were to be applied? And my final question would be that if two objects have the same acceleration, are they under the influence of equal forces? This is probably only true if the masses of the objects are the same, but I just wanted to be sure. Any help with these questions would be great.
Thanks!

 

[Doc Al]

Hi,
I was hoping someone could help me with some general net force questions that will help me answer some of my problems. For example, if a net force acts on an object, does the object's speed and/or velocity change? Furthermore, is the net force that acts on an object which remains at rest equal to zero?

Newton's 2nd law tells us that $F_{net} = m a$. Now apply it to your two questions. (1) If there's a net force on an object, it must be accelerating. (What does acceleration mean?) (2) If an object remains at rest, what is it's acceleration? Thus, what must be the net force on it?

Going off of the velocity question from above, will a car, for example, initially moving at a constant velocity slow down unless a small net force were to be applied?

If the net force on the car were zero, the car would never slow down (or turn). In real life, friction and air resistance act on the car to slow it down. So an additional force must be applied to balance those forces. When you are driving down a straight road at constant speed, Newton's law tells you that all the forces acting on the car (air resistance, the ground, gravity, etc.) must add to zero.

And my final question would be that if two objects have the same acceleration, are they under the influence of equal forces? This is probably only true if the masses of the objects are the same, but I just wanted to be sure.

Once again, turn to Newton. If an object is accelerating, the net force on it must equal "mass x acceleration". So the net force must be greater on the more massive object.

 

[thepatientmental]

Hi there! I'd be happy to help you with your net force questions. Here are the answers:

1. If a net force acts on an object, its speed and/or velocity will change. This is because a net force causes acceleration, which is defined as a change in velocity over time.

2. Yes, the net force acting on an object at rest is equal to zero. This is because an object at rest has no acceleration, and according to Newton's First Law of Motion, an object at rest will remain at rest unless acted upon by an external force.

3. Yes, a car moving at a constant velocity will slow down if a small net force is applied. This is because the net force will cause a change in the car's velocity, resulting in a change in its speed.

4. If two objects have the same acceleration, they are under the influence of equal forces. This is true even if the masses of the objects are different. This is because the acceleration of an object is directly proportional to the net force acting on it, and the mass of an object is inversely proportional to its acceleration. Therefore, if two objects have the same acceleration, they must also have the same net force acting on them.

I hope this helps clarify things for you. Let me know if you have any other questions. Best of luck!