I study physics and I cannot find the following themes (they are quite similar) anywhere in physics textbooks: Problem 1: I drive my car (without a seatbelt) with a velocity v and my body mass is m. Suddenly I collide in a unmovable wall. Consider my car to be completely stiff. Due to the conservation of momentum my body will continue to move forward with a velocity v and I will have a kinetic energy of K = 1/2 mv^2. On the wall is installed vertically a well adjusted scale. What is the indication of the scale when my body eventually stops on it (the scale) relatively to my body weight (B = mg) ? If I apply the conservation of energy theorem: 1/2 mv^2 = 1/2 kx^2 (where k is the scale's constant and x the spring's movement) I find a result which depends on k or x which doesn't seem right to me [F = (v / sqrt(xg)) * B where B is my gravitational force and F is the force created from the collision]. The reason is that every scale should show the same indication regardless of its k or x. Can anyone give me the right equation ? Problem 2: I jump from h meters above the ground to the previous scale. What would be the scale's indication (the higher one) relatively to my weight ? Forgive my poor english.