帮我解答这道题目，并用动画形式展现。---4. 如图甲所示, t=0时质量m=0.1kg的小球在水平向右的拉力F作用下由静止开始从水平面AB的左端向右运动, t=4s时从B端水平飞出后, 从D点无碰撞的进入位于同一竖直面内的光滑圆轨道, 并恰好能到达圆轨道的最高点E后水平飞出。已知小球与水平面AB之间的动摩擦因数μ=0.2, B、D两点之间的高度差h=0.45m、水平距离x=1.2m, 小球所受拉力F与其作用时间t的关系如图乙所示, 重力加速度g取10m/s², 忽略空气阻力, 求: 甲: [Diagram showing a horizontal surface AB, a step down to C, and a smooth curved track DE. A ball is shown on the horizontal surface at point A with a force F acting horizontally to the right. Points A, B, C, D, E, O are labeled. An arrow labeled F points to the right from the ball. The curved track is a segment of a circle with center O and highest point E. Point D is at the entrance of the curved track, likely at the bottom.] 乙: [Line graph showing the relationship between force F (in N) and time t (in s). The Y-axis is labeled F/N and the X-axis is labeled t/s. A straight line goes from (0, F₀) to (4, 0). The origin is labeled 0. The point on the X-axis where the line crosses is labeled 4.] (1)小球到B点时的速度大小v_B; (2)t=0时拉力F的大小F₀; (3)圆轨道半径R。 **Extraction Content:** **Question Stem:** As shown in Figure 甲, at t=0, a small ball with mass m=0.1kg starts from rest at the left end of the horizontal surface AB under the action of a horizontal rightward force F and moves to the right. At t=4s, after being horizontally launched from end B, it enters a smooth circular track located in the same vertical plane from point D without collision, and just reaches the highest point E of the circular track before being launched horizontally. It is known that the kinetic friction coefficient between the ball and the horizontal surface AB is μ=0.2, the height difference between points B and D is h=0.45m, and the horizontal distance is x=1.2m. The relationship between the force F acting on the small ball and its action time t is shown in Figure 乙. Take the gravitational acceleration g as 10m/s². Neglect air resistance. Calculate: **Given Parameters and Information:** * Mass of the ball: m = 0.1kg * Initial condition: Starts from rest at t=0 at the left end of AB. * Force F is horizontal and to the right. * At t=4s, the ball is horizontally launched from B. * From point D, the ball enters a smooth circular track without collision. * The track is in the same vertical plane. * The ball just reaches the highest point E of the circular track. * Kinetic friction coefficient between the ball and surface AB: μ = 0.2 * Height difference between B and D: h = 0.45m * Horizontal distance between B and D: x = 1.2m * Gravitational acceleration: g = 10m/s² * Air resistance is neglected. * The relationship between F and t is given by the graph in Figure 乙. **Diagram 甲 Description:** * **Type:** Schematic diagram of a physical setup. * **Elements:** * A horizontal surface labeled AB, indicated by hatching below, representing the ground. * A step down from B to C. * A smooth curved track DE, which is a segment of a circle with center O and highest point E, connected at point D. The track is below the level of AB. * A small ball is shown on the horizontal surface AB. * A force F is shown acting horizontally to the right on the ball, represented by an arrow. * Labeled points: A (left end of AB), B (right end of AB), C (point below B after the step), D (entrance to the curved track), E (highest point of the curved track), O (center of the circular track). * The line OD and OE are indicated as dashed lines, suggesting radii or vertical/horizontal lines related to the center. **Diagram 乙 Description:** * **Type:** Line chart. * **Elements:** * Y-axis labeled F/N, representing the force F in Newtons. * X-axis labeled t/s, representing time t in seconds. * A straight line graph extending from the point (0, F₀) on the Y-axis down to the point (4, 0) on the X-axis. * Labeled points: 0 (origin), 4 (on the X-axis), F₀ (on the Y-axis). * The line represents a linear decrease of force F from F₀ at t=0 to 0 at t=4s. **Questions to be Calculated:** (1) The magnitude of the velocity of the small ball at point B, v_B. (2) The magnitude of the force F at t=0, F₀. (3) The radius R of the circular track.