Final answer:
Smacking your forehead impacts the frontal bone of the skull, which is a part of the brain case that protects the brain. Strong blows to the head can be hazardous and potentially lead to fractures and brain injuries.
Step-by-step explanation:
If you smack your forehead with the palm of your hand because you don't know the answers to a test, you are impacting your frontal bone.
The frontal bone is one of the bones that makes up the front part of the skull and is part of the brain case that encloses and protects the brain.
It is important to note that strong blows to the head can be dangerous and can cause various types of fractures, such as linear, comminuted, depressed, or contrecoup fractures, potentially leading to serious brain injuries such as hematomas if blood vessels are impacted.