A 6.5 kg rock thrown down from a 120m high cliff with initial velocity 18 m/s down. Calculate the following ATTENTION：using the energy/work formulae only: 3.The kinetic energy of the Rock half way down ？ 4.the speed of the Rock half way down？
5.The speed of the Rock as it hits the ground？

The midpoints? a, b, and c are marked on the histogram. match them to the indicated scores. which? scores, if? any, would be considered? unusual?

For problems 1-3, consider a simple dc brush motor with a permanent magnet stator. with an an consider a simple dc brush motor with a permanent magnet ae supply voltage of 100 v, the no-load speed of the motor is 1000 rpm. this motor can provide a torque of 1.9 n-m at 800 rpm drawing a current of 2 a current are both zero at no load.) 1. with an armature supply voltage of 100 v, the motor is operated at 900 rpm. what is the motor torque? what is the mechanical power delivered by the motor? what is the current draw? what is the electrical power input? what is the energy efficiency of the motor? with an armature supply voltage of 100 v, the motor is operated at 1100 rpm (where it acts as a generator). what torque input is required? what mechanical power is required what current is generated? what is the electrical power generated? what is the energy efficiency of the motor acting as a generator? 2. with an armature supply voltage raised to 120 v, the motor is operated at 1000 rpm. what is the no-load speed? what is the motor torque? what is the mechanical power delivered by the motor? what is the current draw? what is the electrical power input what is the energy efficiency of the motor? 3.

What do you think car designers do if the damage caused by a crash test is too severe?