1. The problem statement, all variables and given/known data A player swinging a tennis racket comprises a very heavy flat object (the racket-arm body combination) which makes a head-on collision with a very light object (the 2 ounce ball). The ball leaves the racket according to the formula: Vball = ε × Vracket The United States Tennis Association imposes a rule on ball manufacturers: σ = 1.5 If the racket is moving at 60 mph, how fast does the ball come off the racket? How fast would a player have to swing the racket in order for the serve to come off the racket at 120 mph? A superball will come off a heavy racket with ε = 1.9 How fast does it come off a racket moving at 70 mph? 2. Relevant equations All are stated. 3. The attempt at a solution I'm having trouble conceptualizing this problem. In addition, the added information, σ = 1.5 confuses me because that symbol, σ, appears nowhere in the equation. Also, how many solutions are required? 3? The way I see it, I need to see how fast the ball comes off the racket if the racket is moving at 60mph (solution 1). I have to see how fast a player would have to swing the racket in order for the serve to come off the racket at 120 mph (solution 2). And I have to figure out how fast the ball comes off a racket moving at 70 mph (solution 3). The added information about the "superball" is really confusing me as well. Is the weight of the ball 1.9 or is the weight of the ball 2.0? I'm very confused about the constants I should be using. So for instance, for the first part of the question: "If the racket is moving at 60 mph, how fast does the ball come off the racket?" Vball = ε × Vracket Vball = ε × 60 but what is E? is it 1.5, or 2 oz?