As part of your daily workout, you lie on your back and push with your feet against a platform attached to two stiff ideal springs arranged side by side so that they are parallel to each other. when you push the platform, you compress the springs. you do 70.0 j of work when you compress the springs 0.200 m from their uncompressed length. what magnitude of force must you apply to hold the platform in this position? how much additional work must you do to move the platform a distance 0.220 m farther? what maximum force must you apply to move the platform a distance 0.220 m farther?

Review multiple-concept example 7 in this chapter as an aid in solving this problem. in a fast-pitch softball game the pitcher is impressive to watch, as she delivers a pitch by rapidly whirling her arm around so that the ball in her hand moves in a circle. in one instance, the radius of the circle is 0.626 m. at one point on this circle, the ball has an angular acceleration of 66.1 rad/s2 and an angular speed of 12.6 rad/s. (a) find the magnitude of the total acceleration (centripetal plus tangential) of the ball. (b) determine the angle of the total acceleration relative to the radial direction.