The New England Merchants Bank Building in Boston is 152 m high. On windy days it sways with a frequency of 0.12 Hz , and the acceleration of the top of the building can reach 1.6 % of the free-fall acceleration, enough to cause discomfort for occupants.

Car batteries are often rated in amp-hours. this rating indicates the quantity of charge that can pass through the battery before the battery's chemical energy must be restored by the car's generator or some other source. the amp-hour unit is convenient for simple calculations. for example, a 60-amp-hour battery can supply a current of 1.0 a for 60 h (or 60 a for 1.0 h) before going dead. find the energy stored in the following. (a) a 58 a-h, 10 v car battery(b) a 1.3 a-h, 1.7 v flashlight battery