Uma pedra de gelo a 0*c é colocado em 200g de água à 30*c, num recipiente térmico desprezível e isolado termicamente. o equilíbrio térmico se estabelece em 20*c (dados: valor específico da água c=1.0 cal/g.*c; calor latente de fusão do gelo l=80 cal/g.*c). qual é a massa da pedra de gelo?

In raising a 6200-n piano with a pulley system, the movers note that, for every 2.2 m of rope pulled down, the piano rises 0.12 m . ideally, find the force required to lift the piano.

Why is alternating current more effective at long–distance travel than direct current? a. the power lines are made out of conductors. b. transformers increase or decrease voltage as needed. c. the ac generator is more efficient. d. ac has lower voltage than dc.

The experiment done in lab is repeated, using a ball that has unknown mass m. you plot your data in the form of f 2 versus m/l, with f in rev/s, m in kg, and l in m. your data falls close to a straight line that has slope 3.19 m/(kg · s2). use g = 9.80 m/s2 and calculate the mass m of the ball.