Finding Net Force in Physics Homework

[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?"

Homework Equations

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.

 

[rl.bhat]

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?

 

[AEM]

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.

 

[dois]

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
?

 

[jamesweston0]

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.

 

[dois]

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?

 

[AEM]

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.

 

[dois]

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]

 

[AEM]

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.

 

[dois]

alright, thank you!

 

[AEM]

You are quite welcome.