9. A person pushes two boxes with a horizontal 100N force on a frictionless floor. Box A is heavier than box B. Which of the following statement is correct? A 100N B a) Box A pushes on box B with a force of 100N, and box B pushes on box A with a force of 100N b) Box A pushes on box B harder than box B pushes on box A c) Boxes A and B push on each other with equal forces of less than 100N d) The boxes will not begin to move unless the total weight of the two boxes is less than 100N

the most common type of reef is the fringing reef. this type of reef grows seaward directly from the shore. they form borders along the shoreline and surrounding islands.

the answer is: the „power stroke“ step.

muscle contraction can be divided into a few steps:

1. the release of ach (acetylcholine) in the synaptic cleft, binding of ach for its receptor and consequently opening of the ca channels.

2. the release of ca, binding of ca for the troponin

3. troponin shifting the tropomyosin, which was blocking the active site on the actin

4. myosin heads attaching to actin by breaking down atp to adp+ pi

5.   formation of the ‘cross-bridge’ on the active site of the actin filament by myosin head

6. “power stroke” -the cross bridge pulls actin, which slides over the myosin

9.     7. the release of adp completes the cross-bridge movement and atp attaches to myosin, breaking the actin-myosin cross bridge.