A 52.9-kg skateboarder starts out with a speed of 2.04 m/s. He does 116 J of work on himself by pushing with his feet against the ground. In addition, friction does -264 J of work on him. In both cases, the forces doing the work are non-conservative. The final speed of the skateboarder is 6 m/s. a. Calculate the change in the gravitational potential energy. b. How much has the vertical height of the skater changed, and is the skater above or below the starting point?

Aplane flies directly between two cities, a and b, which are separated by . from a to b, the plane flies into a headwind. on the return trip from b to a, the wind velocity is unchanged. the trip from b to a takes less than the trip from a to b. what is the airspeed of the plane, assuming it is the same in both directions

Which changes of state do the labels represent? a: b: c:

Researchers conducted an experiment to identify the effects of three different hand sanitizers on the growth of bacteria. the researchers grew one type of bacteria in twenty-four identical covered petri dishes. then, they opened eighteen petri dishes and applied the three hand sanitizers to six petri dishes each. they left the remaining six petri dishes closed as a control group. when the researchers measured the growth of bacteria two days later, the six dishes that had no hand sanitizer showed the least amount of bacterial growth. the researchers concluded that not using any hand sanitizer would lead to the least bacterial growth. which statement best explains why the researchers’ conclusion was not justified? the experiment tested too many variables. the control group was not treated the same as the experimental group. the sample size of twenty-four petri dishes is not large enough. the single type of bacteria is not adequate to make any conclusions.