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Vectors and matrices — Question 8

QCAA 2025, Paper 1 · 1 mark

Q8 · 2025 · Technology-freeSimple familiar1 mark

QUESTION 8

The position vectors of two objects over time,

t

, where

t\ge0

, are given by

\mathbf r_1(t)=-2\hat{\mathbf i}+t^2\hat{\mathbf j}

and

\mathbf r_2(t)=at\hat{\mathbf i}+4\hat{\mathbf j}

(where

a\in\mathbb R

). Given that the two objects collide, the value of

a

is

(A)

2

(B)

1

(C)

-1

(D)

-2

ABCD

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