Tension of string holding one mass to a wall, on top of another moving mass?

[finniusmorgan]

Hello!
This is my first post, I am taking an introductory physics course during my second semester of college and having some trouble with this problem. I hope I have followed the correct format, I appreciate any help that can be offered!

Homework Statement

A 4.82 kg block is placed on top of a 10.7 kg
block. A horizontal force of F = 69.7 N is
applied to the 10.7 kg block, and the 4.82 kg
block is tied to the wall. The coefficient of
kinetic friction between all moving surfaces
is 0.197. There is friction both between the
masses and between the 10.7 kg block and the
ground.
The acceleration of gravity is 9.8 m/s2 .

Homework Equations

F=ma
f= [coefficient of friction]*Fn

The Attempt at a Solution

I really don't know how to find the normal forces that are used in finding the frictional force, but after that I would subtract the friction from the horizontal force to find the net force on the bottom (10.7kg) object, but I do not understand how to relate that to the tension in the string holding the second object.

Thank you!

 

[sArGe99]

Hint : The frictional force between the blocks acts in different directions for the bodies. Tension can be calculated from it..

 

[nlightner]

I would first start by identifying the key variables and forces involved in this problem. We have two masses, a horizontal force, and friction. The horizontal force is applied to the 10.7 kg block, causing it to accelerate. This acceleration will also affect the 4.82 kg block on top of it. The frictional force is dependent on the coefficient of friction and the normal force, which is the force exerted by one surface on another when they are in contact. In this case, we have two surfaces in contact - the two blocks and the bottom block and the ground.

To find the normal forces, we can use the equation F=ma. Since we know the mass and acceleration of the 10.7 kg block, we can find the normal force exerted by the ground on it. We can then use this normal force to calculate the frictional force between the two blocks, using the equation f=[coefficient of friction]*Fn. This will give us the frictional force acting on the 10.7 kg block.

Next, we can use the horizontal force and the frictional force to calculate the net force on the 10.7 kg block. This net force will also act on the 4.82 kg block on top of it. However, since the 4.82 kg block is tied to the wall, it will not accelerate horizontally. This means that the tension in the string holding the block to the wall must be equal and opposite to the horizontal force acting on the 4.82 kg block. We can use the equation F=ma to find the tension in the string.

In summary, we can use the equations F=ma and f=[coefficient of friction]*Fn to find the normal forces and frictional forces involved in this problem. Then, we can use the equation F=ma to find the net force on the 10.7 kg block, and use this to determine the tension in the string holding the 4.82 kg block to the wall. I hope this helps!