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floor, a worker of weight 0.800 kN pushes horizontally with a force of 0.300 kN

ID: 2038726 • Letter: F

Question

floor, a worker of weight 0.800 kN pushes horizontally with a force of 0.300 kN on a box weighing 1.80 kN. As a result of this push, find the magnitude acceleration of the worker and the box. 3) Two blocks are connected by a string that goes over an ideal pulley as shown in the figure. Block A has a mass of 4.00 kg and can slide over a rough plane inclined 30.0° to the horizontal. The coefficient of kinetic friction between block A and the plane is 0.400. Block B has a mass of 3.00 kg. What is the acceleration of the blocks?

Explanation / Answer

2)Mass of worker = 800 N/9.81 = 81.55 kg

mass of box = 1800/9.81 = 183.49 kg

Fnet = 300 N

a(worker) = 300/81.55 = 3.68 m/s^2

a(box) = 300/183.49 = 1.63 m/s^2

Hence, a(worker) = 3.68 m/s^2 ; a(box) = 1.63 m/s^2

3)We can write for the hanging mass:

mBg - T = mB a

for mass on incline

T - mAg sin(theta) - uk mB g cos(theta) = mA a

from the above two eqn we get

a = (mB g - mA g sin(theta) - uk mB g cos(theta))/(mA + mB)

a = (3 x 9.81 - 4 x 9.81 x sin30 - 0.4 x 4 x 9.81 x cos30)/(3 + 4) = -0.54 m/s^2

Hence, a = -0.54 m/s^2