Solved: PHYSICS Question for NEET

NEET PHYSICSEasy

A car moves from X to Y with a uniform speed vᵤ and returns to X with a uniform speed v_d. The average speed for this round trip is:

2v_d vᵤ / (v_d + vᵤ)

√(vᵤ v_d)

v_d vᵤ / (v_d + vᵤ)

(vᵤ + v_d) / 2

Recall Definition: Average speed is defined as the total path length divided by the total time interval . $v_{avg} = \frac{\text{Total Path Length}}{\text{Total Time}}$
Define Variables: Let the distance between X and Y be $d$ . For the trip from X to Y: Speed = $v_u$ , Distance = $d$ , Time $t_1 = \frac{d}{v_u}$ . For the return trip from Y to X: Speed = $v_d$ , Distance = $d$ , Time $t_2 = \frac{d}{v_d}$ .
Calculate Totals: Total Path Length = $d + d = 2d$ . Total Time = $t_1 + t_2 = \frac{d}{v_u} + \frac{d}{v_d} = d \left( \frac{1}{v_u} + \frac{1}{v_d} \right) = d \left( \frac{v_d + v_u}{v_u v_d} \right)$ .
Calculate Average Speed: $v_{avg} = \frac{2d}{d \left( \frac{v_d + v_u}{v_u v_d} \right)}$ $v_{avg} = \frac{2 v_u v_d}{v_u + v_d}$ (This is the harmonic mean of the speeds).

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