1. The problem statement, all variables and given/known data A tennis ball of mass = 0.060 kg and speed = 26 m/s strikes a wall at a 45° angle and rebounds with the same speed at 45° . 2. Relevant equations Δp = pfinal - pinitial horizontal velocity = (26 m/s)cos 45° There's a picture if you all care. 3. The attempt at a solution pintial = mv pintial = (0.060 kg)cos 45° pinitial = 1.1028 kgm/s pfinal = - pintial I made this relationship because it is now going in the opposite direction. pfinal = -1.1028 kgm/s Δp = -1.1028 kgm/s - 1.1028 kgm/s = -2.2056 kgm/s The answer is positive and I cannot understand why. What is the direction of the impulse given to the ball? A. Upward B. Downward C. Left D. Right I've eliminated B and C but I'm still unsure. The sine and cosine of forty-five degrees are the same.