1. ENERGY PROBLEMS STUDENTS: RAÚL, MARCOS, PAULA, AINOA AND MARTA

2. PROBLEM 1 Paula is out with her friends. Misfortune occurs and Paula and her friends find them selves getting a workout. They apply a comulative force of 1080 N to push the car 218 m to the nearest fuel station. Determine the work done no the car. W = F x d W = 1080 x 218 = 235440 J = 2,35 x 10 5 J

3. PROBLEM 2 While training for breeding season, a 380 g male squirrel does 32 pushups in a minute, displacing its center of mass by a distance of 8.5 cm for each pushup. Determine the total work done on the squirrel while moving upward (32 times). E p = m x g x h E p = 0,38 x 0,085 x 9,8 = 0,31654 W = F x d W = 0,31654 x 32 = 10,12988 J

4. PROBLEM 3 During de Powerhouse lab, Jerome runs up the stairs, elevating his 102 kg body a vertical distance of 2,29 in a time of 1,32 s at the constant speed. Determine the power generated by Jerome. P = W / (t f – t i ) P = (102 x 9,8 x 2.29) / 1,32 = 1734,15 W = 1,73 x 10 3 W

5. PROBLEM 4 How much heat is needed to raise the temperature of 2 kg of copper from 20º C to 70º C? Given: m=2 kg; T=70º C – 20º C= 50º C; c= 3,9 x 10 2 J/kg Q = m x c x (T f – T i ) Q = 2 x 3,9 x 10 2 x 50 = 3,9 x 10 4 J

6. PROBLEM 5 According with a scientific research performed recently, Italy needs to push photovoltaic cells technology along 1861 km 2 to face the demand of electric energy. The italian territory covers 301.338 km 2. Which percentage of italian territory need to cover with photovoltaic celles to face the italian energy consumption requirements? % = (1861 / 301.338) x 100 = 0,6 %

7. PROBLEM 6 A wind generator with 30 meters blades supply 1500 KW power. If average daily electric requirement per family is equal to 1,5 KW, how many families is a single generator able to satisfy the demand of? families = 1500 / 1,5 = 1000 families