Note that the same result would be obtained if the impulse J were applied anywhere along the line through P in the direction of J. The point P is called the center of percussion associated with the center of motion Example Striking a billiard ball We want to know at what height above the table does a billiard ball have to be hit so that rolls on the table without slippin R Since the moment of inertia of a homogeneous sphere about its center of mass is IG=(2/5)mR, if we want the instantaneous center of motion to be at C, the height above g, dpr, should be d pr IG/m R h=R+d ADDITIONAL READING J. L. Meriam and L G. Kraige, Engineering Mechanics, DYNAMICS, 5th Edition 6/8 References [1 M. Martinez-Sanchez, Unified Engineering Notes, Course 95-96Note that the same result would be obtained if the impulse J were applied anywhere along the line through P in the direction of J. The point P ′ is called the center of percussion associated with the center of motion C. Example Striking a billiard ball We want to know at what height above the table does a billiard ball have to be hit so that rolls on the table without slipping. Since the moment of inertia of a homogeneous sphere about its center of mass is IG = (2/5)mR2 , if we want the instantaneous center of motion to be at C, the height above G, dP ′ , should be, dP ′ = IG/m R = 2 5 R , and h = R + dP ′ = 7 5 R . ADDITIONAL READING J.L. Meriam and L.G. Kraige, Engineering Mechanics, DYNAMICS, 5th Edition 6/8 References [1] M. Martinez-Sanchez, Unified Engineering Notes, Course 95-96. 5