I jerked back and sat down hard on the ground.
He doubled over and sat down hard on a chair.
That is going to hurt like anything in a bit, she thought, and sat down hard.
Suddenly all the strength went out of his legs and he sat down hard.
Then David stopped and sat down hard on the edge of his bed.
He dropped him to the ground and sat down hard.
She sat down hard on the chair he had left pulled out from the table.
He fell against the door jam, and sat down hard.
She sat down hard on the first thing that looked like it might be real.
His feet got tangled, and he sat down hard, instead.