On a roller coaster ride the total mass of the cart - with passengers included - is 305 kg. Peak K is at 47.0 m above the ground, peak L is at 21.5 m. The speed of the cart at K is 15.1 m/s, at L it is 12.7 m/s. (The wheel mechanism on roller coaster carts always keeps the carts safely on the rail.) How much energy is lost due to friction between the two peaks?

In an old-fashioned amusement park ride, passengers stand inside a 3.0-m-tall, 5.0-m-diameter hollow steel cylinder with their backs against the wall. the cylinder begins to rotate about a vertical axis. then the floor on which the passengers are standing suddenly drops away! if all goes well, the passengers will “stick” to the wall and not slide. clothing has a static coefficient of friction against steel in the range 0.60 to 1.0 and a kinetic coefficient in the range 0.40 to 0.70. part a what is the minimum rotational frequency, in rpm, for which the ride is safe? express your answer using two significant figures. f f = rpm