You are out and about in the country and your father sees a rock that he really wants in the yard. now you must get the very heavy rock into the back of a
truck. the truck bed is 3 feet off the ground. your father pulls out a 5-foot plank and begins to set up a ramp. at the same time, you (who know about
mechanical advantage! ) have found a plank that is 8 feet long, and you show it to your father.
which plank will give you the most mechanical advantage? calculate the ma for each plank.

As a car drives with its tires rolling freely without any slippage, the type of friction acting between the tires and the road is 100) a) static friction. b) kinetic friction. c) a combination of static and kinetic friction. d) neither static nor kinetic friction, but some other type of friction. e) it is impossible to tell what type of friction acts in this situation.

It is really hard for me right know

Arunner is jogging at a steady 3.6 km/hr. when the runner is 2.9 km from the finish line, a bird begins flying from the runner to the finish line at 14.4 km/hr (4 times as fast as the runner). when the bird reaches the finish line, it turns around and flies back to the runner. even though the bird is a dodo, we will assume that it occupies only one point in space, i.e., a zero-length bird. how far does the bird travel? (b) after this first encounter, the bird then turns around and flies from the runner back to the finish line, turns around again and flies back to the runner. the bird repeats the back and forth trips until the runner reaches the finish line. how far does the bird travel from the beginning? (i.e. include the distance traveled to the first encounter)