So again, I need help with physics. It is real tough to learn because my teacher doesnt teach haha. First, is a problem based on the work-energy theorem and kinetic energy. A fighter jet is launched from an aircraft carrier with the aid of its own engines and a steam-powered catapult. The thrust of the engines is 2.3 x 10^5N. In being launched from rest it moves through a distance of 87 m and has a kinetic energy of 4.5 x 10^7 J at lift-off. What is the work done on the jet by the catapult? -- the answer is 2.5 x 10^7 J -- can anyone tell me how to get it? And then A 16kg sled is being pulled along a horizontal snow-covered ground by a horizontal force of 24 N. Starting from rest, the sled attains a speed of 2.0 m/s in 8 m. find the coefficient of kinetic friction between the runners of the sled and the snow. -- the answer is 0.13 --can anyone tell me how to get it? +rep if you show me how to do either
1. The jet has a final kinetic energy of 4.5 x 10^7 J. The work done by the engines is F*d = (2.3 x 10^5)*87 So 4.5 x 10^7 = (2.3 x 10^5)*87 + Work done by the catapult Work done by the catapult = 2.5 x 10^7 J 2. The final kinetic energy of the sled is KE = 1/2 mv^2 = 1/2 * 16 * 2^2. That equals the amount of work done by the person pulling - the friction (its minus because friction does "negative" work) So 1/2 mv^2 = Work done by the puller - Work done by friction = F*d - F_friction*d 1/2 * 16 * 2^2 = 24*8 - (mu*mg)*8 32 = 192 - mu*16*10*8 mu = 0.13