Two cyclists, A and B

MATHEMATICS · Multi-part · A Level · Mathematics · Kinematics · Kinematics

Problem

Two cyclists, A and B, ride along a straight, flat track that is aligned with the positive xx-axis. • Cyclist A starts at t=0t=0 seconds from x=0x=0 meters and travels with velocity vA(t)=2t+2v_A(t)=2t+2 meters per second for t≥0t\ge 0. • Cyclist B starts from the same point 3 seconds later. For B the time variable τ\tau is defined so that τ=0\tau=0 when B begins. B’s velocity is vB(τ)=4τ+1v_B(\tau)=4\tau+1 meters per second for τ≥0\tau\ge 0. Throughout the problem let tt denote the number of seconds elapsed since AA started (so t≥0t\ge 0). (1) Express Cyclist B’s position xBx_B as a function of the global time variable tt for t≥3t\ge 3. State both the functional form and the value of xBx_B at t=3t=3. Include appropriate units. (2) For t≥3t\ge 3, determine the exact time tt (to three decimal places) at which the two cyclists are at the same position. Justify that this time is the only solution with t≥3t\ge 3. (3) Calculate the velocity of each cyclist at the meeting time found in part (b). Provide units and indicate the direction of motion relative to the positive xx-axis. (4) Interpret your results from parts (b) and (c) in context. Explain whether the meeting represents B overtaking A from behind or a head-on encounter, and identify which cyclist is traveling faster at the instant they meet.

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