Answer:External forces are forces caused by external agent outside of the system. Internal forces are forces exchanged by the objects in the system.
Explanation:or our purposes, we will simply say that external forces include the applied force, normal force, tension force, friction force, and air resistance force. And for our purposes, the internal forces include the gravity forces, magnetic force, electrical force, and spring force.HOPE THIS HELPS!!! ^w^
I think it’s d but I’m not sure
Answer:
7.23407 
Explanation:
(I will not include units in calculations)
I'm assuming FBD's are already drawn, so I will work from there.
Let the 2.2kg block equal
, and the 20kg block equal
.
Summation equation for
:
, 
Summation equation for
: 
Torque Summation Equation: 
Do some plugging in with the values given: 
Replace
with
, and cancel out the r's.
This step is important: Rearrange the force summation equation to solve for each tension force.

Perform Substitution: 
Now, we need to find the friction force and the horizontal component of the force of gravity.
Note that
μ
And based on our earlier summation equation: 
First, break
into x and y components.
, 
Perform substitution with this and the fact that
.

Solving for a, plugging in numbers yields an answer of 7.23407 