At t=0 car A passes point O with speed 10 m/s and acceleration 2 m/s². Five seconds later car B passes O with constant speed 30 m/s. Consider motion after B passes O. Which statements are correct?
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Question

At t=0 car A passes point O with speed 10 m/s and acceleration 2 m/s². Five seconds later car B passes O with constant speed 30 m/s. Consider motion after B passes O. Which statements are correct?

G1 Physics · Accepted Answer

When B reaches O (take this as τ=0), A is at 75 m with speed 20 m/s. Relative position x_A−x_B=75−10τ+τ². Its discriminant is 100−300<0, so B never overtakes A. Relative velocity=−10+2τ becomes zero at τ=5 s; separation is then minimum. Afterwards A pulls away. Thus A, C and D are correct.