High school physics forces help

[BobTheScience]

I'm trying to understand forces a bit more, but i have questions that I've been searching online for and can't find an answer. My questions:
Question 1. is Fnet = ma? Because I'm doing some questions my teacher gave us and the explanations say to use F=ma, not Fnet. F and Fnet aren't the same things, so how come they have the same formula?

Question 2. If the static friction of an object is 10N, would applying 10N of force move the object at a constant speed, or will it still stay at rest?

Question 3. If every action causes an opposite and equal reaction, why do objects move? If i apply a 20N force on an object, shouldn't it apply a 20N force back, which would mean the Fnet is 0 and it shouldn't move.

Question 4. One of my questions from homework: A 20N object is sliding from left to right and the force of friction is 2.4N. The object stops moving after traveling 10 meters. Find the acceleration of the object.
The answer is: acceleration is equal to 1.2m/s^2. The explanation given was:
Fnet = 2.4N
Fnet = ma
2.4N = (20N/9.8m/s^2) * a
a = 1.2m/s^2

I understand everything about the problem, but one thing. Why can i assume that the Fnet is 2.4N? It says that the Force of Friction is 2.4N, not the Fnet. The force of friction could be 2.4N, while the Fapplied could be anything less than 2.4N. So why do we assume that Fapplied is 0N?Relevant Topics/Formulas:
Forces
Fnet = ma

The Attempt at a Solution

Really confused about all 4.

Thank you for reading this, any help is appreciated.

 

[SteamKing]

At PF, we have rules governing HW questions. You should have read these upon joining.

One of these rules is that PF prefers its users post one HW question per thread, not an entire list of unrelated questions. Having one question per thread keeps replies on point and is less confusing. PF also requires posters to show an attempt at answering posted questions. Saying "I don't know." or similar is not sufficient.

 

[Doc Al]

Question 1. is Fnet = ma? Because I'm doing some questions my teacher gave us and the explanations say to use F=ma, not Fnet. F and Fnet aren't the same things, so how come they have the same formula?

It should be F_net = ma, but if there's only one force acting, then F_net = F.

Question 2. If the static friction of an object is 10N, would applying 10N of force move the object at a constant speed, or will it still stay at rest?

Generally, static friction will be whatever is needed to prevent motion up to some maximum value. If that maximum value were 10 N, you would have to apply a force greater than 10 N to get it to move.

Question 3. If every action causes an opposite and equal reaction, why do objects move?

Those forces act on different objects.

If i apply a 20N force on an object, shouldn't it apply a 20N force back,

It does.

which would mean the Fnet is 0 and it shouldn't move.

The F_net on which object?

Question 4. One of my questions from homework: A 20N object is sliding from left to right and the force of friction is 2.4N. The object stops moving after traveling 10 meters. Find the acceleration of the object.
The answer is: acceleration is equal to 1.2m/s^2. The explanation given was:
Fnet = 2.4N
Fnet = ma
2.4N = (20N/9.8m/s^2) * a
a = 1.2m/s^2

I understand everything about the problem, but one thing. Why can i assume that the Fnet is 2.4N? It says that the Force of Friction is 2.4N, not the Fnet. The force of friction could be 2.4N, while the Fapplied could be anything less than 2.4N. So why do we assume that Fapplied is 0N?

Since no applied force is even mentioned, it is reasonable to assume there is none.

 

[BobTheScience]

Thank you Doc for all your help.

 

[HalfLostAndSearching]

Hello,
I can provide some insight into your questions about forces in high school physics.

1. The equation Fnet = ma is a simplified version of Newton's second law of motion, which states that the net force acting on an object is equal to the mass of the object multiplied by its acceleration. This equation is often used in introductory physics courses to help students understand the relationship between force, mass, and acceleration. F and Fnet can be used interchangeably in this equation because Fnet represents the net force, which is the sum of all the individual forces acting on an object. So, if there is only one force acting on an object, then F and Fnet will be the same.

2. In order for an object to move at a constant speed, the net force acting on the object must be equal to zero. So, if the static friction of an object is 10N, then applying 10N of force will not move the object at a constant speed. The object will still remain at rest because the net force is still 10N (10N applied force - 10N friction force = 0N net force). In order for the object to move at a constant speed, the applied force must be greater than the static friction force.

3. The statement "every action causes an opposite and equal reaction" is referring to Newton's third law of motion. This law states that for every action, there is an equal and opposite reaction. In the example you gave, if you apply a 20N force on an object, the object will apply a 20N force back on you. However, this does not mean that the object will not move. This is because the object also has other forces acting on it, such as gravity or friction, that can cause it to move.

4. In this problem, the Fnet is equal to the force of friction (2.4N) because there are no other forces acting on the object. The object is only moving in one direction (from left to right), so there is no net force in the vertical direction (up or down). Therefore, the net force is equal to the force of friction, which is acting in the opposite direction of the motion. We can assume that the Fapplied is 0N because the problem states that the object is sliding, which means that there is no applied force pushing or pulling on it. If there was an applied force