PLEASE HELP ME A 3.0 cm tall object is 15 cm away from a concave mirror with a focal point of 5.0 cm. If the image is 7.5 cm from the mirror, what is the image height? -1.5 cm
O -0.5 cm
-3.0 cm
-6.0 cm
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Three point charges, two positive and one negative, each having a magnitude of 20 μc are placed at the vertices of an equilateral triangle (30 cm on a side). what is the magnitude of the electrostatic force on the negative charge

Cathy is pedaling down a steep hill on her bicycle and wants to be able to coast up the next hill, which is 25 meters high, without pedaling. cathy and her bicycle have a mass of 75 kg. assuming her bicycle is 100% efficient, what would her speed have to be?

The voltage applied across a given parallel-plate capacitor is doubled. how is the energy stored in the capacitor affected?