John and Dave are having a disagreement about where to place a new refrigerator in their kitchen. As shown in (Figure 1), John is applying a FJ = 220 N force to the right, and Dave is pushing back in the opposite direction with a force FD. The fridge has a mass m = 80 kg. The coefficient of static friction between the fridge and the floor is μs=0.40, and the kinetic coefficient is μk=0.20. How hard would Dave have to push in order to get the fridge moving to the left (initial moment)? Assume that John continues to apply a 220 N force to the right.

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)