my misconception? replied by popikachu @ Fri, 09 May 2008 23:46:58 +0800

popikachu — Fri, 09 May 2008 23:46:58 +0800

Originally posted by eagle:

simplified example

your legs push you forward at 20 N

And you push the box at 5N

So the force pushes back to you at 5N

And so your net forward force is 15N

And in your case, the 5N gives acceleration forward of 1m/s^2 for the box, and the 15N also gives you acceleration forward of also 1m/s^2. Thus, you will "stay" with the box.

i thought it is the friction that is against you and not the box?

lol
i haven study til so far... haha

my misconception? replied by annoy-you-must @ Thu, 01 May 2008 14:49:08 +0800

annoy-you-must — Thu, 01 May 2008 14:49:08 +0800

Originally posted by aiglosicicle:

even by using your logic you are wrong. using your logic ONLY... by right when you push the crate nothing will happen because the force you apply and the normal contact force acting against you is equal and they cancel out. you wont be moving backwards.

in the real world forces of friction exist between you and the floor and also between the box and the floor. due to the difference in the friction that is why when you push the box the box moves and you move along.

You cannot cancel out forces that way in the first place too. The forces acting on the box by me and the forces acting on me by the boxes are acting on different bodies, and forces acting on different bodies cannot be canceled out.

my misconception? replied by aiglosicicle @ Sun, 27 Apr 2008 20:07:52 +0800

aiglosicicle — Sun, 27 Apr 2008 20:07:52 +0800

Originally posted by annoy-you-must:

There's a stationary crate on the ground. I push the crate. Since I'm applying a force on the crate, the crate is asserting the same amount of force on me in the opposite direction...therefore, I should experience acceleration in the direction that is opposite from the acceleration of the box. I should be moving away from the crate once i push it.

But this defies logic since I can push the crate and stay with it at the same time. So what's wrong with my conception here?

even by using your logic you are wrong. using your logic ONLY... by right when you push the crate nothing will happen because the force you apply and the normal contact force acting against you is equal and they cancel out. you wont be moving backwards.

in the real world forces of friction exist between you and the floor and also between the box and the floor. due to the difference in the friction that is why when you push the box the box moves and you move along.

my misconception? replied by eagle @ Sun, 27 Apr 2008 02:33:09 +0800

eagle — Sun, 27 Apr 2008 02:33:09 +0800

it is actually net force on a body

must recognize that the box and the human are two separate bodies, and the forces acting upon them are purely on the body in question

my misconception? replied by purpledragon84 @ Sun, 27 Apr 2008 02:29:36 +0800

purpledragon84 — Sun, 27 Apr 2008 02:29:36 +0800

basically its the friction between ur feet and the ground that is making all this possible la.. haha.. if u in space u push the box de hua u will float away from the box and the box away from u mah..

my misconception? replied by eagle @ Sun, 27 Apr 2008 02:23:36 +0800

eagle — Sun, 27 Apr 2008 02:23:36 +0800

Originally posted by Kuali Baba:

You left out friction between your feet and the ground, and that between the box and the ground.

simplified version mah

consider too many later confuse

my misconception? replied by Kuali Baba @ Sun, 27 Apr 2008 02:15:41 +0800

Kuali Baba — Sun, 27 Apr 2008 02:15:41 +0800

You left out friction between your feet and the ground, and that between the box and the ground.

my misconception? replied by eagle @ Sun, 27 Apr 2008 02:05:36 +0800

eagle — Sun, 27 Apr 2008 02:05:36 +0800

simplified example

your legs push you forward at 20 N

And you push the box at 5N

So the force pushes back to you at 5N

And so your net forward force is 15N

And in your case, the 5N gives acceleration forward of 1m/s^2 for the box, and the 15N also gives you acceleration forward of also 1m/s^2. Thus, you will "stay" with the box.

my misconception? replied by ChoCoChips @ Sat, 26 Apr 2008 18:41:07 +0800

ChoCoChips — Sat, 26 Apr 2008 18:41:07 +0800

wah this one so long liao i kind of forgot already.

but i think u muz take into the masses into consideration? ie newtons 2nd law.

say u exert a force f.

both u n the crate oso experience this force.

but since u have a heavier mass, the acceleration on u is small, while the acceleration on the crate is larger.

heh i dunno correct anot.

my misconception? replied by annoy-you-must @ Sat, 26 Apr 2008 18:19:32 +0800

annoy-you-must — Sat, 26 Apr 2008 18:19:32 +0800

There's a stationary crate on the ground. I push the crate. Since I'm applying a force on the crate, the crate is asserting the same amount of force on me in the opposite direction...therefore, I should experience acceleration in the direction that is opposite from the acceleration of the box. I should be moving away from the crate once i push it.

But this defies logic since I can push the crate and stay with it at the same time. So what's wrong with my conception here?

Recent Posts in 'my misconception?' | sgForums.com