How is the acceleration of objects on an inclined plane determined?

[leisiminger]

Homework Statement [/b]
Objects of Masss m1= 4kg and m2 = 9kg are connected by a light string that passes over a frictionless pulley. Object m1 = is held at rest on the floor, and m2 rests on a fixed incline of 40 degrees. The objects are released from rest, and m2 slides 1 meter down the <b>rough</b> incline in 4 seconds.
a) determine the acceleration of each object using a kinematic equation for constant acceleration b) the tension in the string, and d) the coefficient of kinetic friction between m2 and the incline.

I'm really having trouble finding the acceleration, I'm not sure if I am looking too deeply into it.

 

[tiny-tim]

Welcome to PF!

Objects of Masss m1= 4kg and m2 = 9kg are connected by a light string that passes over a frictionless pulley. Object m1 = is held at rest on the floor, and m2 rests on a fixed incline of 40 degrees. The objects are released from rest, and m2 slides 1 meter down the <b>rough</b> incline in 4 seconds.
a) determine the acceleration of each object using a kinematic equation for constant acceleration b) the tension in the string, and d) the coefficient of kinetic friction between m2 and the incline.

I'm really having trouble finding the acceleration, I'm not sure if I am looking too deeply into it.

Hi leisiminger! Welcome to PF!

Is the incline a ramp that leads upward to the floor?

If not, can you explain the set-up?

Anyway, tell us what principles you've tried, and where you're stuck, and then we'll know how to help.

 

[leisiminger]

hi,
Thanks!

https://www.physicsforums.com/attachment.php?attachmentid=2614&d=1109446369
is a good picture of the problem, except that m1 starts on the floor at rest.

well, to be honest, i thought about just analyzing one block, since acceleration will be the same on both blocks, using a = Vf-Vo / t. Vf being .25 m/sec ( 1 m / 4 sec ), Vo being zero, and time being 4 sec.



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[tiny-tim]

well, to be honest, i thought about just analyzing one block, since acceleration will be the same on both blocks, using a = Vf-Vo / t. Vf being .25 m/sec ( 1 m / 4 sec ), Vo being zero, and time being 4 sec

Hi leisiminger!

I think you'll have to do an equation for each block, and combine them to get your kinematic equation.

Hint: call the acceleration a, and the tension T.

 

[leisiminger]

i don't understand, the acceleration of one block should be the acceleration of the other block right? The velocity of an object under constant acceleration will increase linearly and is:
vf = v0 + a t

 

[tiny-tim]

i don't understand, the acceleration of one block should be the acceleration of the other block right? The velocity of an object under constant acceleration will increase linearly and is:
vf = v0 + a t

oh I see what you're doing …

yes, if you assume the acceleration, a, is constant, then you can calculate a without using m1 m2 or theta …

but you need an equation with s and t, not v and t. ​

 

[leisiminger]

any more help, just a clue?

 

[tiny-tim]

any more help, just a clue?

oh come on …

s = … ? ​

 

[leisiminger]

we use a,v,x,and t. i assume your mean x for change in distance? if so, its 1m

 

[leisiminger]

ok, i have an idea. would i use

a = m1g -m2gsin theta
-------------------
m1 + m2