# Finding Net Force in Physics Homework

• dois
In summary, the person experienced a net force of 64 kg m/s when pulled by the horse at a speed of 1.6 m/s.
dois

## Homework Statement

the questions says,
"Person A who's mass is 40kg, is being pulled across the ground by a horse at a speed of 4 m/s [E]. All of a sudden the horse accelerates for a period of 5 seconds. During this time person A experiences a displacement of 40 m [E]. What net force was experienced by person A?"

## The Attempt at a Solution

I have no idea how to even begin this question. I'm not sure what equations i even need to use.

Hi dois, welcome to PF.
In the problem the initial velocity, duration pof acceleration and the displacement is given. Can find find a kinematic equation from the textbook which relates these quantities with acceleration?

dois said:

## Homework Statement

the questions says,
"Person A who's mass is 40kg, is being pulled across the ground by a horse at a speed of 4 m/s [E]. All of a sudden the horse accelerates for a period of 5 seconds. During this time person A experiences a displacement of 40 m [E]. What net force was experienced by person A?"

Here is a little more help. This can be approached as a two step question. Recall that Newton's second law says F = ma. You have the mass of the person so you need the acceleration. You can find the acceleration from the information given in the problem using a kinematics equation that relates distance, velocity, time, and acceleration.

ok so first I would need to find the acceleration so I can sub that answer into F= m*a
so i would use
acceleration= v/t
?

dois said:
ok so first I would need to find the acceleration so I can sub that answer into F= m*a
so i would use
acceleration= v/t
?

The problem gives you the initial speed (Vi), time (t), and displacement (d). If you take a look at the kinematic equations, you'll find that you can solve one of them for acceleration. The kinematic equation you're looking for is this one.

d = (vi)(t) + (1/2)(a)(t)^2

Go from there.

Ok so if we sub all of our know variables into the equation
d = (vi)(t) + (1/2)(a)(t)^2
then we would get:
40= 4x5 +1/2 (?) x5^2
40=20 +25/2 x
20=25/2 x
20=12 1/2 x
x= 1.6

but as soon as i figure out the acceleration where do I go from there to find out the net force?

Last edited:
dois said:
Ok so if we sub all of our know variables into the equation
d = (vi)(t) + (1/2)(a)(t)^2
then we would get:
40= 4x5 +1/2 (?) x5^2
40=20 +25/2 x
20=25/2 x
20=12 1/2 x
x= 1.6

but as soon as i figure out the acceleration where do I go from there to find out the net force?

Okay, your algebra looks good, so a = 1.6 m/sec squared.

Remember I said this was a two step question. Go back and read my first post. That indicates what you do next.

So then we would sub a into F=ma
so (40kg) (1.6 m/s)
and then our answer would be Fnet= 64 kg m/s [E]

That should do it, except that the units you give are wrong. The seconds should be squared. That combination of units has its own name: Newtons.

alright, thank you!

You are quite welcome.

## 1. What is net force in physics?

Net force in physics refers to the overall force acting on an object or system. It is the resulting force from all the individual forces acting on the object, considering both the magnitude and direction of each force.

## 2. How do I find the net force in a physics problem?

To find the net force, you need to first identify all the individual forces acting on the object. Then, you need to add up all the forces in the same direction and subtract any forces in the opposite direction. The resulting value is the net force.

## 3. What is the unit of net force in physics?

The unit of net force in physics is Newtons (N). It is a derived unit, which means it is composed of other base units such as mass, length, and time.

## 4. Can the net force on an object be zero?

Yes, the net force on an object can be zero if all the individual forces acting on the object cancel each other out. This means that the object is either at rest or moving at a constant velocity.

## 5. How does finding net force relate to Newton's laws of motion?

Finding the net force is an essential step in applying Newton's laws of motion. According to the first law, an object will remain at rest or in motion at a constant velocity unless acted upon by a net force. The second law states that the net force acting on an object is directly proportional to its acceleration. Therefore, finding the net force allows us to analyze and understand an object's motion based on these laws.

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