What is the change in the skaters kinetic energy? A skater is a mass of 50 kg slides across an icy pond with negligible friction. As he approaches a friend, both he and his friend hold out their hands, and the friend exerts a force in the direction opposite to the skaters movement, which slows the skaters speed from 2.0 m/s2 to 1.0 m/s2.
The correct answer is option B – 75 joules Since kinetic energy= 0.5mv^2 KE1 = (0.5(50)(2^2) = 100 KE2 = (0.5(50)(1^2) = 25 To calculate the KE at the two different velocities then subtract them. KE = (0.5(50)(2^2)) - (0.5(50)(1^2)) = 100-25 = 75 kgm/s^2 Keep in mind that kilogram meters per second squared (kgm/s^2) is the same as Joules ~ 75 Joules.