12. A boy of mass 50 kg running 5m/s jumps on to a 20kg trolley

travelling in the same direction at 1.5m/s. Find their common

velocity. Assume that there is no external unbalanced force

working in the horizontal direction.

A typical student listening attentively to a physics lecture has a heat output of 100 w. how much heat energy does a class of 170 physics students release into a lecture hall over the course of a 50 min lecture?

Kelly sits on a rock. Her weight is an action force. What is the reaction force?

The energy of microwaves is less than the energy of ultraviolet light. Which comparison of the energies of electromagnetic waves is correct? A. Gamma rays have higher energy than microwaves because gamma rays have shorter wavelength. B.

The brakes of a 125 kg sled are applied while it is moving at 8.1 m/s, which exerts a force of 261 N to slow the sled down. How far does the sled travel while coming to a stop in meters? Round to one decimal place.

Which of theses statements are true about the theory of plate tectonics and the theory of continental drift A) The theory of plate tectonics doesn't explain how continental movements could occur B) The theory of tectonics tells exactly where the

A pendulum bob is made from a sphere filled with water. What would happen to the frequency of vibration of this pendulum if the sphere had a hole in it that allowed the water to leak out slowly?

Elias serves a volleyball at a velocity of 16 m/s. The mass of the volleyball is 0.27 kg. What is the height of the volleyball above the gym floor when its total mechanical energy is 41.70 J? Round to the nearest number.

Which of the following is the best description of a graph? A. Equations that can be plotted B. A representation of an equation C. Independent and dependent variables D. x and y lines

Which of the following statements concerning Howard Gardner's multiple intelligences is not correct? A. Gardner is not interested in assessing levels of intelligence. B. Gardner has based his theory on research in various areas of psychology. C.

The force of attraction between two oppositely charged pith balls is 5.3 * 10-6 newtons. If the charge on the two objects is 6.7 * 10-9 coulombs, what is the distance between the two charges? (k = 9.0 * 109 newton·meter2/coulombs2)