What is the function of the commutator in a dc motor

A2000 kg car is rounding a curve of radius 200 m on a level road. the maximum frictional force the road can exert on the tires of the car is 4000 n. what is the highest speed at which the car can round the curve?

Astone is dropped from a cliff and falls 9.44 meters. what is the speed of the stone when it reaches the ground? a. 13.6 m/sec b. 1.39 m/sec c. 185 m/sec d. 9.80 m/sec

In a heat engine if 1000 j of heat enters the system the piston does 500 j of work, what is the final internal energy of the system if the initial energy was 2000 j? 1. write the equation 2.list out your known variables 3.plug the numbers into the equations 4.solve 5.write your solution statement that includes initial energy and final