please 3,6,9,45

3-11 A vertical plate is submerged (or partially submerged) in water and has the indicated shape. Explain how to approximate the hydrostatic force against one side of the plate by a Riemann sum. Then express the force as an integral and evaluate it. 3. 4. 3 ft 2 ft 5 ft 8 ft 10 ft 2 ft 5. 1 4 m 6. 4 m 8 m 12 m 7. 8. 3 ft 6 m 6 ft 5 ft 5 ft 4 m 9. 4 ft 10. $ 1 ft a a 2 ft 8 ft a 11. 2a h aEXAMPLE 4 Find the center of mass of a semicircular plate of radius r with uniform density. SOLUTION In order to use (8) we place the semicircle as in Figure 11 so that y= Vr2-x2 f(x) = vr2 - x2 and a = -r, b = r. Here there is no need to use the formula to 4r calculate x because, by the symmetry principle, the center of mass must lie on the 317 y-axis, so x = 0. The area of the semicircle is A = 3 Tr2, so -r 0 X FIGURE 11 = . 1 1, ( voz - xz ) dx 2 = ['(2 - x3 ) dx (since the integrand is even) x' = 3 2 273 4r = 3 3 TT The center of mass is located at the point (0, 4r/(3TT)).46. The solid obtained by rotating the triangle with vertices (2, 3), (2, 5), and (5, 4) about the x-axis VA 0 X44-46 Use the Theorem of Pappus to find the volume of the given solid. 44. A sphere of radius r (Use Example 4.) 45. A cone with height h and base radius