Mr. Draper asks his class to design a system of gears, strings, and pulleys that will allow him to pull back the classroom's curtains simply by turning a crank at his desk. The system must be built within the following constraints:
It must be made only out of metal gears, metal pulleys, string, and one crank.
It must be strong enough to move the curtains.
It cannot be in the way of students or their desks.
It must take no more than one day to build.

The final design will use which type of energy to perform work on the curtains?
A.
elastic potential energy
B.
gravitational potential energy
C.
thermal energy
D.
kinetic energy

Abatter hits the baseball a with an initial velocity of v0 = 110 ft/sec directly toward fielder b at an angle of 23° to the horizontal; the initial position of the ball is 2.2 ft above ground level. fielder b requires 0.44 sec to judge where the ball should be caught and begins moving to that position with constant speed. because of great experience, fielder b chooses his running speed so that he arrives at the “catch position” simultaneously with the baseball. the catch position is the field location at which the ball altitude is 8.4 ft. determine the velocity of the ball relative to the fielder at the instant the catch is made.

Two point charges are on the y axis. a 3.90-µc charge is located at y = 1.25 cm, and a -2.4-µc charge is located at y = −1.80 cm. (a) find the total electric potential at the origin. v (b) find the total electric potential at the point whose coordinates are (1.50 cm, 0). v

If a rock is thrown upward on the planet mars with a velocity of 12 m/s, its height (in meters) after t seconds is given by h = 12t − 1.86t2. (a) find the velocity of the rock after two seconds. m/s (b) find the velocity of the rock when t = a. 12−3.72a m/s (c) when will the rock hit the surface? (round your answer to one decimal place.) t = s (d) with what velocity will the rock hit the surface? m/s