# Physics

posted by .

What is the acceleration of the upper block? The coefficient of kinetic friction between the lower block and upper block is 0.0005. The coefficient of kinetic friction between lower block and floor is 0.0001. Upper block is 1kg, lower block is 2kg, and Force of 20N is applied to lower block.
Here's a picture:

img217.imageshack.us/img217/3526/2505100050.jpg

I got 20 m/s as the acceleration of the upper block. Is this right?

• Physics -

Sorry here's the picture:

img245.imageshack.us/img245/3526/2505100050.jpg

• Physics -

No; it's not right. First of all, 20 m/s is a speed, not an acceleration.

The two masses accelerate at different rates because there is very little friction and the top mass tends to be left behind. The top mass (#2) is accelerated only by the kinetic friction force between the blocks, which is
0.0005 M2 g = M2*a2, so
a2 = 0.0005 g = .0049 m/s^2
and the force that accelerates M2 is just M2 a2 = 0.0049 N

The force that accelerates M1 is
20N - (3 kg)(0.0001)g - 0.0049 = M1*a1
20N - .0029N - .0049N = 2 a1
a1 = 9.996 m/s^2

• Physics -

Thank you! I see where I went wrong

## Similar Questions

1. ### physics

The coefficient of static friction is 0.604 between two blocks. The coefficient of kinetic friction between the lower block and the floor is 0.115. Force F causes both blocks to cross a distance of 3.93 m, starting from rest. What …
2. ### Physics

A lower block is being pulled to the right across a wooden table and it is 5kg and the block on top of it weighs 2 Kg. The friction between the table and the lower block is reduces the total acceleration to be 1.5 m/s2. Friction keeps …
3. ### Physics

A 0.5 kg wooden block is placed on top of a 1.0 kg wooden block. The coefficient of static friction between the two blocks is 0.35. The coefficient of kinetic friction between the lower block and the level table is 0.2. What is the …
4. ### Mechanics

A 30.0-kg block is resting on a flat horizontal table. On top of this block is resting a 15.0-kg block, to which a horizontal spring is attached, as the drawing illustrates. The spring constant of the spring is 325 N/m. The coefficient …
5. ### physics

A 30.0-kg block is resting on a flat horizontal table. On top of this block is resting a 15.0-kg block, to which a horizontal spring is attached, as the drawing illustrates. The spring constant of the spring is 340 N/m. The coefficient …
6. ### physics

A block M1 of mass 16.5 kg sits on top of a larger block M2 of mass 26.5 kg which sits on a flat surface. The kinetic friction coefficient between the upper and lower block is 0.425. The kinetic friction coefficient between the lower …
7. ### Physics

A block M1 of mass 13.0 kg sits on top of a larger block M2 of mass 23.0 kg which sits on a flat surface. The kinetic friction coefficient between the upper and lower block is 0.440. The kinetic friction coefficient between the lower …
8. ### Physical science

Two rectangular blocks are stacked on a table. The upper block has a mass of m2 and the lower mass is m1 > m2. The coefficient of kinetic friction between the lower block and the table is ųk. The coefficient of static friction …
9. ### Physics

A block M1 of mass 20.0 kg sits on top of a larger block M2 of mass 30.0 kg which sits on a flat surface. The kinetic friction coefficient between the upper and lower block is 0.415. The kinetic friction coefficient between the lower …
10. ### Physics

A 27.0-kg block is resting on a flat horizontal table. On top of this block is resting a 13.0-kg block, to which a horizontal spring is attached, as the drawing illustrates. The spring constant of the spring is 310 N/m. The coefficient …

More Similar Questions