A thin uniform rod of length pivots about its center

PHYSICS · Multi-part · A Level · Physics · Engineering physics · Engineering physics

Problem

A thin uniform rod of length LL pivots about its center. Two small thrusters attached at distances L/4L/4 and L/2L/2 from the pivot apply forces perpendicular to the rod in opposite directions, producing torques of equal magnitude τ0\tau_0 but opposite sign. The thrusters fire according to the schedules: • Thruster A (positive torque): τA(t)=+τ0(1−tT)\tau_A(t) = +\tau_0\left(1 - \frac{t}{T}\right) for 0≤t≤T0 \le t \le T, zero afterward. • Thruster B (negative torque): τB(t)=−τ0(tT)\tau_B(t) = -\tau_0\left(\frac{t}{T}\right) for 0≤t≤T0 \le t \le T, zero afterward. (1) Part 1: (a) Write the algebraic expression for the net torque τnet(t)\tau_{\text{net}}(t) acting on the rod during 0≤t≤T0 \le t \le T. (2) Part 2: (b) Derive an expression for the angular displacement Δθ\Delta\theta of the rod during the firing interval in terms of τ0\tau_0, TT, and the rod’s moment of inertia II. Assume the rod is initially at rest in the horizontal plane. (3) Part 3: (c) Using your result from part (b), determine the total work done on the rod by both thrusters during 0≤t≤T0 \le t \le T. Express your answer solely in symbols. (4) Part 4: (d) Evaluate whether any additional work is done on the rod after t=Tt = T and justify your answer based on the physical situation.

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