فيزياء قانون حفظ الطاقة والاحتكاك Friction on the roller-coaster car. 

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فيزياء قانون حفظ الطاقة والاحتكاك
Friction on the roller-coaster car.
The roller-coaster car shown reaches a vertical height of only 25 m on the second hill before coming to a momentary stop. It traveled a total distance of 400 m.
Determine the thermal energy produced and estimate the average friction force (assume it is roughly constant) on the car, whose mass is 1000 kg.