Give examples of when it might be necessary for one branch to exercise more power than another branch?
The US government, along with others, operates on checks and balances. The legislative, judicial, and executive branch powers are balanced by this system.
For example, the president (part of the executive branch), can veto laws. However, the other two branches can issue what is known as the 2/3 vote to show the majority's opinion, which keep the president's power in check.