The mass of an object varies directly with the potential energy of the object and inversely with the height of the object off the ground. a 25-kg object has 980 joules of potential energy when it is 4 meters off the ground. another object has 150 joules of potential energy at 3 meters off the ground. what is the mass of the second object?
0.32 kilograms
2.88 kilograms
5.10 kilograms
45.90 kilograms

Martha has a deck of cards. she has lost some of the cards, and now the deck only contains nine spades, eleven diamonds, eight clubs, and twelve hearts. martha predicts that whenever she draws a card from the deck without looking, she will draw a club one-fifth of the time. which activity would best allow martha to test her prediction? a. randomly draw a card from the box and see if it is a club. b. randomly draw a card. then, continue to draw another card until all eight clubs are drawn. c. randomly draw and replace a card 120 times. then, observe how close to 30 times a club is drawn. d. randomly draw and replace a card 100 times. then, observe how close to 20 times a club is drawn.