# Three Blocks on Frictionless Incline(Please check work)

• ryan1180
In summary, the conversation discusses a situation where three blocks are pushed up a frictionless plane with constant acceleration. The masses of the blocks are given, and three questions are asked about the situation. The first question asks about the magnitude of the forces exerted by the blocks on each other, and the correct answer is false. The second question compares the forces exerted by block A and block C on block B, and the correct answer is that FAonB is greater than FConB. The final question asks for the value of the external force exerted on block A, and the correct answer is 31.6 N, calculated using F=ma.
ryan1180

## Homework Statement

Three blocks are pushed up a frictionless plane that is inclined at an angle of 30 degrees with respect to the horizontal as shown below. The blocks move together with constant acceleration a = 3.0 m/s2. The masses of the blocks are: MA = MC = 1 kg, and MB = 2 kg. The next three questions pertain to this situation.

[PLAIN]https://online-s.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?courses/phys100/fall10/hwb/06/01/fig4.gif

The magnitude of the force that block A exerts on Block B is greater than the magnitude of the force that block B exerts on Block A.

TRUE
FALSE

Compare FAonB, the force Block A exerts on Block B, to FConB, the force Block C exerts on Block B,

FAonB < FConB
FAonB = FConB
FAonB > FConB

What is the value of F, the external force that is exerted on Block A?

F = 3.0 N
F = 4.9 N
F = 12.0 N
F = 31.6 N
F = 39.2 N

Fnet=ma
(Newton's laws)

## The Attempt at a Solution

I have found answers for the questions, I'd just like my work to be checked

Part 1:
False, because Newton's second says for each force there is an equal and opposite reaction, therefore meaning the forces must be equal
Part 2:
Faonb>Fconb
Looking at the diagram, Faonb is greater because it has the forces of two blocks acting on it as opposed to just one in Fconb, follow Newton's second again.
Part 3:
I used F=ma
F-40sin(30)=4(3)
to get 31.6 N

If anyone could check my work it would be much appreciated!

Last edited by a moderator:
It's almost correct, you miscalculated part 3. F = ma + mgsin30 = 4*3 + 4*10*0.5 = 12+20 = 32N. I don't know how you got 31.6...

EDIT: sorry, I didn't realize part 3 also had options:) Yeah 31.6 is correct, but in your equation it shouldn't be 40sin(30), but 4*9.81*sin(30), you get 31.6 that way.

Yeah, I had calculated it with 10 m/s^2 and then changed it to 9.8 but forgot to change it on my note sheet that I'm working the problems out on.

Thanks!

## What is the Three Blocks on Frictionless Incline experiment?

The Three Blocks on Frictionless Incline experiment is a physics experiment that involves three blocks of different masses placed on a frictionless incline. The blocks are connected by strings and the incline is set at a specific angle. The objective of the experiment is to observe the motion of the blocks and analyze the forces acting on them.

## What equipment is needed for the Three Blocks on Frictionless Incline experiment?

The equipment needed for this experiment includes three blocks of different masses, strings, a frictionless incline, a protractor to measure the angle of the incline, a ruler to measure the distance, and a stopwatch to measure the time.

## What are the main principles behind the Three Blocks on Frictionless Incline experiment?

The main principles behind this experiment are Newton's laws of motion, specifically the laws of inertia and acceleration, as well as the concepts of friction and inclined planes. These principles help explain the motion of the blocks and the forces acting on them.

## How do you calculate the acceleration of the blocks in the Three Blocks on Frictionless Incline experiment?

To calculate the acceleration of the blocks, you can use the formula a = (m1+m2+m3)gsinθ / (m1+m2+m3)+m1m2+m2m3+m1m3), where m1, m2, and m3 are the masses of the blocks and θ is the angle of the incline. This formula takes into account the forces of gravity and tension acting on the blocks.

## What are the potential sources of error in the Three Blocks on Frictionless Incline experiment?

Some potential sources of error in this experiment include the accuracy of the equipment used, such as the incline and protractor, and external factors such as air resistance. It is also important to ensure that the strings connecting the blocks are taut and that the incline is truly frictionless for accurate results.

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