Hi, let me ask probably dumb questions to physics experts... Why does the cue ball goes almost straight when its right (or left) side is struck by a cue (right English)? This is quite different from when a ball hits another ball, in which case the ball goes almost perpendicular from the contact surface. Here, I want to focus on the ball direction immediately after the impact and ignore the curve after the ball starts to roll. I heard that it is because the ball and cue can be thought as unity so the force only propagates to the cue direction. But if so, would it be possible that the cue makes the ball spin? My guess is that the friction between the ball and cue tip makes the ball not only spin but also go to the right direction and counteracts the force perpendicular from the contact surface (left), resulting that the ball goes to the cue direction? I heard that the friction coefficient is pretty high ~0.6. Any comments will be appreciated!