A59-kg woman eats a 583 calorie (583 kcal) jelly doughnut for breakfast. (a) how many joules of energy are the equivalent of one jelly doughnut? j (b) how many steps must the woman climb on a very tall stairway to change the gravitational potential energy of the woman-earth system by a value equivalent to the food energy in one jelly doughnut? assume the height of a single stair is 15 cm. stairs (c) if the human body is only 29% efficient in converting chemical potential energy to mechanical energy, how many steps must the woman climb to work off her breakfast? stairs

Aparticle's position is given by x = 3.00 - 9.00t + 3t2, in which x is in meters and t is in seconds. (a) what is its velocity at t = 1 s? (b) is it moving in the positive or negative direction of x just then? (c) what is its speed just then? (d) is the speed increasing or decreasing just then? (try answering the next two questions without further calculation.) (e) is there ever an instant when the velocity is zero? if so, give the time t; if not, answer "0". (f) is there a time after t = 3 s when the particle is moving in the negative direction of x? if so, give the time t; if not, answer "0".