The 1.0 kg block in the figure is tied to the wall with a rope. It sits on top of the 2.0 kg block. The lower block is pulled to the right with a tension force of 20 N. The coefficient of kinetic friction at both the lower and upper surfaces of the 2.0 kg block is μk = 0.490.

i have found the tension in rope one is 4.8 (though my math gave me a negative 4.8, mastering physics wanted a positive for some strange reason). Now i need to find the acceleration of block 2.... T2=20; N=mg=19.6. -fk+T2=ma. i have -.490(19.6)+20=2a. solve for a gives me the wrong answer. why?

Question

The 1.0 kg block in the figure is tied to the wall with a rope. It sits on top of the 2.0 kg block. The lower block is pulled to the right with a tension force of 20 N. The coefficient of kinetic friction at both the lower and upper surfaces of the 2.0 kg block is μk = 0.490.

i have found the tension in rope one is 4.8 (though my math gave me a negative 4.8, mastering physics wanted a positive for some strange reason).  Now i need to find the acceleration of block 2....  T2=20; N=mg=19.6.  -fk+T2=ma.  i have -.490(19.6)+20=2a.  solve for a gives me the wrong answer.  why?

anonymous · Answer

Figure ?

anonymous · Answer

there's a picture, but it's not really needed.  the description explains it

anonymous · Answer

attachment

anonymous · Answer

The answer is 0.2 m/s^2. Right ?

anonymous · Answer

Actually the block is under three forces, 20N right, friction between 2 kg and lower surface to left and 2kg and 1kg to left.

anonymous · Answer

i don't know what the answer is. how did you get that?

anonymous · Answer

See the forces |dw:1403277082271:dw|