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The position vector of a particle changes with time according to the relation ⃗r(t) = 15t²̂i + (4 - 20t²)̂j. What is the magnitude of the acceleration at t = 1 s?

Asked in JEE Main 9th April 2nd Shift 2019 · Acceleration in a plane

• (1) 25
• (2) 40
• (3) 100
• (4) 50

Step-by-step solution

Why the other options are wrong

• (1) Uses the coefficients 15 and 20 without differentiating: √15² + 20² = 25.
• (2) Reports only the y-component of the acceleration.
• (3) No single slip gives 100; the components 30 and 40 combine to 50.

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