L Lizzy A New member Jun 10, 2009 #1 across a room? ?? and A 1-kilogram rock is dropped from a cliff 90 meters high. After falling 20 meters, the kinetic energy of the rock is approximately ..?
across a room? ?? and A 1-kilogram rock is dropped from a cliff 90 meters high. After falling 20 meters, the kinetic energy of the rock is approximately ..?
I [email protected] New member Jun 10, 2009 #3 1. d = rt d = 6 m r = 3*10^8 m/s t is what you want to find t = 2*10^-8 sec. 2. KE = (1/2) mv^2 m = 1 kg v^2 = v0^2 + 2ax v = sqrt(2*9.8*20) = 19.8 m/s KE = (1/2) (1 kg) (19.8 m/s)^2 = 196 J
1. d = rt d = 6 m r = 3*10^8 m/s t is what you want to find t = 2*10^-8 sec. 2. KE = (1/2) mv^2 m = 1 kg v^2 = v0^2 + 2ax v = sqrt(2*9.8*20) = 19.8 m/s KE = (1/2) (1 kg) (19.8 m/s)^2 = 196 J
