A toddler pushed a 4-kg toy car at a constant speed against a ground frictional force of 8 N. Then, the toddler pushed the toy car with the same force on a marble ground with no frictional
force against the toy car, what is the acceleration (in m/s2) of the toy car?
A. 0
B. 1
C. 2
D. 4

A75-hp (shaft output) motor that has an efficiency of 91.0 percent is worn out and is to be replaced by a high-efficiency motor that has an efficiency of 95.4 percent. the motor operates 4368 hours a year at a load factor of 0.75. taking the cost of electricity to be $0.12/kwh, determine the amount of energy and money saved as a result of installing the high-efficiency motor instead of the standard motor. also, determine the simple payback period if the pu