48. A particle moves in the xy-plane in such a way that its velocity vector is \( \langle 1+t,\; t^3 \rangle \). If the position vector at \( t=0 \) is \( \langle 5,0 \rangle \), then the position of the particle at \( t=2 \) is






Answer is: option4

\( \langle 9,4 \rangle \)

Solution:

vector in AP Tutor

\[ \mathbf{v}(t)=\langle 1+t,\; t^3 \rangle \]

\[ \mathbf{R}(t)=\left\langle t+\frac{t^2}{2}+C,\; \frac{t^4}{4}+D \right\rangle \]

When \( t=0 \), \[ \mathbf{R}(0)=\langle C,\;D \rangle \]

Since we are given that \[ \mathbf{R}(0)=\langle 5,\;0 \rangle, \] we know \( C=5 \) and \( D=0 \).

Hence \[ \mathbf{R}(t)=\left\langle t+\frac{t^2}{2}+5,\; \frac{t^4}{4} \right\rangle \]

From this we obtain \[ \mathbf{R}(2)=\langle 9,\;4 \rangle \]

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