Two blocks with masses 4.00 kg and 8.00 kg are connected by string and slide down a 30.0 degree inclined plane.

foass77W

foass77W

Answered question

2020-12-28

Two blocks with masses 4.00 kg and 8.00 kg are connected by string and slide down a 30.0 degree inclined plane. The coefficient of kinetic friction between the 4.00-kg block and the plane is 0.25; that between the 8.00-kg block and the plane is 0.35.
a) Calculate the acceleration of each block
b) Calculate the tension in the string
c) What happens if the positions of the block are reversed, so that the 4.00-kg block is above the 8.00-kg block?
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Answer & Explanation

hajavaF

hajavaF

Skilled2020-12-29Added 90 answers

First note that you must establish a reference frame (i.n. xy plane). For convenience, it is generally assumed that thex-axis is parallel to the slope of the surface and the y-axis is perpendicular to the slope. Furthermore, the positive x-direction is down slope.
Given the above assumptions, now determine the sum of the forces for each block.
m1=4kg mass of block 1
m2=8kg mass of block 2
u1=0.25 coefficient of friction for block 1
u2=0.35 coefficient of friction for block 2
α=30 deg  slope of ramp
g = acceleration due to gravity = 9.8m/s
sum of forces on block 1:
Note that the coefficient of friction is applied to the force normal to the surface
F1=m1gsin(α)u1m1gcos(α)=11.1129 newtons
where m1gsin(α) is the force in the positive x-directionon block 1 due to its weight and m1gcos(α) is the normal force, perpendicular to the slope, due to acceleration of gravity.
Given the sum of forces for F1, its
Jeffrey Jordon

Jeffrey Jordon

Expert2021-10-06Added 2605 answers

n1=m1gcos30

fk1=μk1m1gcos30

m1a1=m1gsin30μk1m1gcos30

a1=9.8(sin300.2cos30)=3.20ms2

n2=m2gcos30

fk2=μk2m2gcos30

m2a2=m2gsin30μk2m2gcos30

a2=9.8(sin300.4cos30)=1.51ms2

b)

m1a1=m1gsin30μk1m1gcos30T

m2a2=m2gsin30μk2m2gcos30+T

T=48(3.21.51)4+8=4.51N

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