How do you determine the magnitude and direction of the net force acting on the object?

Here's the question,,,basic little question I'm having trouble with:
A gust of wind blows an apple from a tree. As the apple falls, the force of gravity on the apple is 9.25 N downward, and the force of the wind on the apple is 1.05 N to the right. Find the magnitude and direction of the net external force on the apple.

So I know it's going to the right at 1.05 N, and downward at 9.25 N. The answer is 4.5m/s^2 to the east. HOW DO YOU GET THAT?!

 

Ok I think I figured out how to do it, could some one confirm if it's correct or not?

I did the pythagorean thereom on 1.05 and 9.25 and got 9.30. I added all of them up, took the square root if it and got 4.5. Is that the way to do it? If so, it took me 1 hr 20 min to figure out. WOW. LOL

 

I've never really heard of converting your magnitude from N to m/s^2, but yes, you need to use the Pythag. theorem.

Find the sum of your Forces in the x direction
Find the sum of your forces in the y direction
(this example you have is a right angle, so you dont have to worry about that)

sq. root ( Fx^2 + Fy^2) = Fr (resultant).

To find the direction:
tan (angle) = Fy/Fx
so:
angle = arctan Fy/Fx

So you should get:
sq. root ( 1.05^2 + 9.25^2)

Thats the way Im being taught it anyway...it seems they are doing it a little differently wherever you are.

 

Thanks for your help

But I calculated the sq root of 1.05squared + 9.25squared and got 9.3... but the answer is 4.5. But um,, the net force I think is another word for acceleration, that's why I think it's in m/s^2.

 

yes, you calculated it right.

When you got 9.3, thats in N.

net force is not necesarrily acceleration. It's just the sum of the forces acting on any specific object (for example, you have two guys pulling a box, each pulling in the opposite direction. First guy is pulling to the right with 100N force, 2nd guy is pulling to the left with 50N force. Your net force is 100 + -50 (-50 because 2nd guy is pulling in the -x direction), so 50N to the right (pretty logical right?)

"Force" (F=ma) is usually described in Neutons (N).
N = mass * acceleration
or
N= kg m/s^2

Now, since you know that gravity acts downward at 9.8 m/s^2, and know the force down, you could probably figure out the mass of the apple, and then resolve the final force into acceleration.

Otherwise, unless you are specifically told to keep your answer in m/s^2, I would use N. Or, if they teach you to solve into m/s^2, do it that way. My teacher just has us keep it in N though (since Force is defined in Neutons).

So, F in the downward direction = 9.25N
F to the right = 1.05N

You already solved the resultant force, (9.30 N), and we can solve for the mass of the apple:
9.25 = m (9.8)
m= 9.25/9.8
m=.9438 kg
so, now we just plug this in with our resultant force:
9.30 = .9438 * a
a= 9.30/.9438
a= 9.8537 m/s^2

SO I really dont know how they got 4.5 m/s^2 :P

But think about it...the apple has to be going at the acceleration of gravity (since its in free fall).

So yeah, Id like to know how they got 4.5 m/s^2 myself
You get this answer from the back of the book?

 

Oh..... never mind, I thought you were looking for a psychic

 

Yes, what he said!

Your target answer cannot be correct. Better copy off of someone else!

 

I thought the title said "Physical People"
Maybe you needed a hand moving a couch or whatever, I was gonna help.

Carry on...

 

Yup, resolve the system into "rectangular components" (i.e., vectors in X and Y in a two dimensional problem) and add them up and then calculate the resultant vector using simple trig.

F=MA, the unit of force is Newtons after that English chap Sir Isaac Newton.

You'll use this method a lot, go ahead and get it down pat.

Good luck.

 

Thanks so much Yeah, I got 4.5 m/s^2 out of the book. The book is often wrong so it could be an error on their part. Do any of you guys have AIM? We could discuss physics on there? It'd be easier.

 

I dont know how much of a help Id be, but if you wish to contact me through AIM my SN is:

SomeGuy82485

 

Consider a force of 66.5N, pulling 3 blocks of identical masses, where each mass is 0.8kg, along a rough horizontal surface. The coefficient of kinetic friction between the blocks and the surface is given by 0.2. The acceleration of the blocks is a. The acceleration of gravity is 9.8m/s^2. Find the acceleration a. Answer in units of m/s^2.

Can someone help me out.

 

Holy 3 year old post Batman if she hasn’t figured it out by now she’s in trouble…

 

Do I detect a romance brewing?

 

Flashbacks... flashbaCks... Must run away and cry... *AHHHHHHHHHHHHHHHHH!*

*jumps off bridge*