i am stuck on two problems: 1.) a sphere is spinning while constantly accelerating in a horizontal position, without friction. How much does it travel in the fifth second, if the constant acceraltion is "x" m/s^2. answers: a.) 12.5x m b.) 8x m c.)25x m d.) 4.5x m e.) 16x m 2.) a cable is lifting a skier that weighs 75 kg to a height of 300m. How much energy is lost when overcoming friction (or inertia?) if the power of the cable is 1.2 kW, and the time to get up to 300 m takes 4 minutes? a.)91kJ b.) 45kJ c.)20kJ d.)150kJ e.)67 KJ Thanks!
1) the fifth second is from t = 4 to t = 5 D = 0.5at^2 so in the 5th second 0.5a(25-16) = 4.5a or 4.5x (d) because a = x 2) work = power x time work = 1200(240sec)= 288kJ Now change in potential energy = mgh = 75(9.81)(300) = 220.725kJ So the amount of resistance = 288 - 220.725 = 67.275 kJ (e)
Intresting