A car starts from rest and accelerates at 5 m s⁻². At t = 4 s, a ball is dropped out of a window by a person sitting in the car. What are the velocity magnitude and acceleration magnitude of the ball at t = 6 s? Take g = 10 m s⁻².
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Question

A car starts from rest and accelerates at 5 m s⁻². At t = 4 s, a ball is dropped out of a window by a person sitting in the car. What are the velocity magnitude and acceleration magnitude of the ball at t = 6 s? Take g = 10 m s⁻².

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G1 Physics · Accepted Answer

Step 1: At t=4 s the car speed is vₓ=at=5×4=20 m s⁻¹; the released ball keeps this horizontal component. Step 2: From t=4 to 6 s, it falls for 2 s, so vᵧ=gt=20 m s⁻¹ downward. Step 3: Speed = √(20²+20²)=20√2 m s⁻¹. Step 4: After release only gravity acts, so acceleration magnitude is 10 m s⁻². Final answer: D.