1. Newton’s First Law (Balanced Forces) Examples
Modified Atwood’s Machine A
Constant Velocity B
Method 1
Treat as two separate objects tied together by a string. A B

2. Newton’s First Law (Balanced Forces) Examples
Example 3 continued
Modified Atwood’s Machine A
Constant Velocity B
Method 1
Begin by writing an equation for the horizontal forces acting on Box A. A B

3. Newton’s First Law (Balanced Forces) Examples
Example 3 continued
Modified Atwood’s Machine A
Constant Velocity B
Write an equation for the vertical forces acting on Box B.
Method 1 A B

4. Newton’s First Law (Balanced Forces) Examples
Example 3 continued
Modified Atwood’s Machine A
Constant Velocity B
Method 2
Treat as a single system since all of the parts move together.
Write an equation for the horizontal forces acting on the system. A B
The Force of Tension is inside the system and can therefore be ignored.