A man on a bike hit by a vehicle sitting on the floor holding his head while others watch.
A man is on injured on the floor while others watch as he waits for medics to arrive.
Sentence 1 doesn't specify that the man is injured and waits for medics to arrive. He could have been waiting for anything, or holding his head in frustration.
exists e2 e3 e1 p1 x1 x2 x3 x4 x5 x6 x7.(n_person(x6) & n_head(x7) & of(x7,x6) & n_male(x6) & n_floor(x6) & a_topic(x1) & on(x1,x2) & Actor(e1,x4) & for(e2,e3) & exists e4 x8.(Actor(e4,x8) & v_watch(e4) & -(x8 = x6) & n_person(x8)) & while(e3,p1) & Theme(e3,x7) & Actor(e3,x5) & v_hold(e3) & on(e2,x6) & Actor(e2,x5) & v_sit(e2) & (x4 = x5) & n_vehicle(x4) & Theme(e1,x3) & v_hit(e1) & (x2 = x3) & n_bike(x2) & n_man(x1))
exists p1 p2 x1 x2.(n_male(x2) & n_person(x2) & n_floor(x2) & exists e1 p3 x4.(exists e2 p4.(Topic(e2,p4) & Actor(e2,x2) & v_wait(e2) & exists e3 x5.(Actor(e3,x5) & v_arrive(e3) & n_medic(x5))) & as(e1,p3) & Actor(e1,x4) & v_watch(e1) & -(x4 = x2) & n_person(x4)) & while(p1,p2) & on(p1,x2) & exists x3.(on(x1,x3) & n_injured(x3)) & n_man(x1))