Check all the boxes that correspond to forces doing zero work gravity acting on a projectile that has been launched straight up
You pushing your stalled car, but it doesn't budge
Drag acting on a plane flying horizontally
gravity acting on your car as it drives horizontally
An olympic weightlifter holding a barbell above their head (the barbell is motionless)
sliding friciton acting on a car slilding to a stop

An athlete swings a ball, connected to the end of a chain, in a horizontal circle. the athlete is able to rotate the ball at the rate of 8.13 rev/s when the length of the chain is 0.600 m. when he increases the length to 0.900 m, he is able to rotate the ball only 6.04 rev/s. (a) which rate of rotation gives the greater speed for the ball? 6.04 rev/s 8.13 rev/s (b) what is the centripetal acceleration of the ball at 8.13 rev/s? m/s2 (c) what is the centripetal acceleration at 6.04 rev/s? m/s2