A car moving with a speed of 54 km/h takes a turn of radius 20 m. A simple pendulum is suspended from the ceiling of the car. Determine the angle made by the string of the pendulum with the vertical during the turning. (Take g=10 m/s²)

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(3) tan⁻¹(1.125). Idea: in the car's frame the bob hangs along the resultant of gravity and the centrifugal pseudo-force, so tan θ=(v²)/(rg). Convert the speed first: v=54 km/h=54×5/(18)=15 m/s. tan θ=(v²)/(rg)=(15²)/(20×10)=(225)/(200)=1.125. θ=tan⁻¹(1.125), about 48°. The bob swings outward, away from the centre of the turn — the same reason a passenger leans outward. Forgetting the km/h conversion is the standard way to lose this one.

A car moving with a speed of 54 km/h takes a turn of radius 20 m. A simple pendulum is suspended from the ceiling of the car. Determine the angle made by the string of the pendulum with the vertical during the turning. (Take g=10 m/s²)

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