# Physics

posted by .

I got two questions

Three blocks on a fricitonless horizontal surface are in contact with each other

a force F is applied to block 1 mass m1

Draw a free body diagram for each block
ok done

the accelration of the system (in terms of m1, m2, and m3)
ok done I got
a = (m1 + m2 + m3)^-1 (force F)

the force of contact that each block exerts on its neighbor
ok no idea how to do this

----->Force F | m1 |--->contact force | m2 |---->contact force | m3 |

ok so how do i do this
ok and

a block (mass m1) on a smooth horizontal surface, connected by a thin cord that passes over a pulley to a second block (m2), which hangs vertically.

Draw a free body diagram for each block showing the force of gravity on each, the force (tension) exerted by the cord, and any normal force

ok done

determine formulas for the acceleration of the system and for the tnesion in the cord. Ignore friction and the masses of the pulley and cord

ok well isn't the force of tension just the opposite in direction but equal in magntiude of the force of gravity on second hanging block?

Also isn't the accleeration zero???

Isn't the net force zero???

ok i do not know how to find the acceleration of the system

• Physics -

Ok I guess I'm drawing the free body diagram wrong how do I draw it because this is not making much sense to me

• Physics -

Why did you start this question by re-asking the three blocks question that we have already explained to you? I assume that you followed directions and are through with that one.

As for the problem with the two masses, cord and pulley: the acceleration is NOT zero in a frictionless situation. The dangling mass m2 exerts a weight force on the cord, which allows both masses to move with the same acceleration, a. What equations of motion have you derived from your FBDs?

The tension force T in the cord does not equal the weight force W = m2*g when the masses are accelerating.

You should have two equations in two unknowns: T and a.

T = m1*a
m2*g - T = m2*a

m2*g = (m1 + m2) a
Solve for a and T

• Physics -

is this right?
------Force F onto m1--->|m1| ---contact force onto m2--->|m2|-----contact force onto m3---->|m3|

• Physics -

No, it is not right. Force and mass have different dimensions.

Mass has to be multiplied by an acceleration rate to get force.

## Similar Questions

1. ### Physics

Three blocks on a frictionless horizontal surface are in contact with each other A force F is applied to block 1 (m1) Draw a free body diagram for each block ok for the diagram is the force F applied horizontal to mass one does this …
2. ### Physics

Ok I got a question I asked before except there are other parts that I didn't ask so here we go Three blocks on a frictionless horizontal surface are in contact with each other A force F is applied to block 1 (mass m1). Draw a free-body …
3. ### Physics

Ok I guess the reason why I do not know how to do this problem is because I can not draw the proper free-body diagram... Three blocks on a frictionless horizontal surface are in contact with each other as shown in Fig. 4-5. A force …
4. ### Physics

Three blocks on a frictionless horizontal surface are in contact with each other, as shown below. A force F is applied to block A (mass mA). (a) Draw a free-body diagram for each block. Determine (b) the acceleration of the system …
5. ### mechanics

Q2. A block of massmrests on the left edge of a block of larger massM. The coefficient of kinetic friction between the two blocks is , and the surface on which the larger block rests is frictionless. A constant horizontal force of …
6. ### physics

A force of 8.7 N is applied to a steel block initally at rest on a horizontal frictionless surface. The force, which is directed at an angle of 30.0o below the horizontal, gives the block a horizontal acceleration of 5.3 m/s2. a) Draw …
7. ### physics

Pleaseee help explain how to draw the free body diagrams for this problem!!! Two blocks with masses m1 = 10.9 kg and m2 = 79.3 kg, shown in the figure (in the figure the 79.3kg block(m2) is on a flat surface, the 10.9kg(m1) block is …
8. ### Physics

A block of mass 3m is placed on a frictionless horizontal surface, and a second block of mass m is placed on top of the first block. The surfaces of the blocks are rough. A constant force of magnitude F is applied to the first block …
9. ### Phys

Three blocks on a frictionless horizontal surface are in contact with each other. A force F is applied to block A (mass mA). (a) Draw a free body diagram for each block. I've drawn it and it looks like this, but I'm not sure if I'm …
10. ### physics

Three blocks on a frictionless horizontal surface are in contact with each other. A force F is applied to block A and the blocks start to slide to the right of their initial position. Determine the acceleration of the system, if m_A …

More Similar Questions