A 60.0 kg object is moving east at 8.00 m/s, and then slows down to 4.00 m/s. How much work was done?

By the work–energy theorem, the work done equals the change in kinetic energy: W = ½m(v_f² − v_i²). Substituting the values gives W = ½(60.0)(4.00² − 8.00²) = 30(16 − 64) = −1,440 J, so the work is negative because the object slowed down. The correct choice is A, −1,440 J.

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