Register to reply

Force being exerted on 3 blocks (ideal situation) calculate force through each object

by EricSomin
Tags: forces, frictionless, mass and weight
Share this thread:
EricSomin
#1
Oct11-11, 10:22 AM
P: 9
1. The problem statement, all variables and given/known data

Blocks with masses of 2kg , 4kg , and 6kg are lined up in a row on a frictionless table. All three are pushed forward by a 60 force applied to the 2 block.

how much force does the 4kg block exert on the 6kg block?

how much force does the 4kg block exert on the 2kg block?


2. Relevant equations

Newtons Laws. and sum of forces.

3. The attempt at a solution

now i understand newtons laws of action and reaction. so im assuming the amount of force acting on the 2kg block from the 4kg block is the same as the 4kg block from the 2kg block.
(wouldnt this mean the system is in equilibrium though?)

anyway, im confused by how to approach this problem. there is no friction, so wouldnt any force at all cause these blocks to start moving?

if there is no friction, why would the force exerted on the 4kg block from the 2kg block be any different than the force exerted directly onto the 2kg block (60.0N).....wouldnt any force cause the system to accelerate since there is no friction to overcome.....

i understand conceptually that m(g) is the force of gravity acting on the block in N. but how would that translate into the loss of force between the blocks of different mass...?


im rambling mostly because im lost with this, how should i begin to approach this problem?

any help at all is greatly appreciated.
Phys.Org News Partner Science news on Phys.org
Final pieces to the circadian clock puzzle found
A spray-on light show on four wheels: Darkside Scientific
How an ancient vertebrate uses familiar tools to build a strange-looking head
1MileCrash
#2
Oct11-11, 10:24 AM
1MileCrash's Avatar
P: 1,304
Try drawing a free body diagram of each block, and marking all forces on each block.
EricSomin
#3
Oct11-11, 10:38 AM
P: 9
Quote Quote by 1MileCrash View Post
Try drawing a free body diagram of each block, and marking all forces on each block.
okay, so i see that for the 2kg block and the 4kg block there is a 3rd law pair. (F of 4 acting on 2) so this will become an internal force

also there is the force from 6kg to 4kg and a force from the 4kg on the 6kg. this is also a 3rd law pair. so i will make it an internal force....

i now have the normal force, and FG for each block, as well as the pushing force (60.0N) on my 2kg block.

would i start by summing the forces in the X direction......if i did that though i would have only 1 force, (force of the push) assuming 3rd law pairs cancel eachother out of the problem...


im guessing i must find a way to make the FG have an effect on the pushing force. but one is in the y direction. and the other is in the x. so how would i make these affect eachother....

Doc Al
#4
Oct11-11, 12:03 PM
Mentor
Doc Al's Avatar
P: 41,555
Force being exerted on 3 blocks (ideal situation) calculate force through each object

Quote Quote by EricSomin View Post
im guessing i must find a way to make the FG have an effect on the pushing force. but one is in the y direction. and the other is in the x. so how would i make these affect eachother....
Treat the x and y directions separately. You can safely assume that there's no acceleration in the y direction.


Register to reply

Related Discussions
Force pushes three blocks, find mag of force exerted on last two blocks Introductory Physics Homework 19
Force exerted on one object by another Introductory Physics Homework 2
Net Force Exerted On A Object? Introductory Physics Homework 4
Two blocks touching with one applied force...how to calculate force of one on another Introductory Physics Homework 3
Contact force in an ideal situation Introductory Physics Homework 4