The position vector of a particle changes with time according to the relation,
\(\vec{r}(t)=(15 t^2) \hat{i}+\left(4-20 t^2\right) \hat{j},\) where \(\vec{r}(t)\) is in metres and \(t\) is in seconds.
What is the magnitude of the acceleration at \(t=1\) second?  
1. \(100\) m/s2 2. \(40\) m/s2
3. \(50\) m/s2 4. \(25\) m/s2
Subtopic:  Acceleration |
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Level 1: 80%+
JEE
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The position vector of a particle is expressed as: \(\overrightarrow{r}\left({t}\right){=}({8}{t}\hat{i}{+}{5}{t}^{2}\hat{j}{+}{6}\hat{k}).\) Which of the following statements correctly describes the direction of the particle’s acceleration?
 
1. It is directed along the positive \({y \text-}\)axis.
2. It is directed along the positive \({x \text-}\)axis.
3. It is equally inclined to the \(x\) and \({y \text-}\)axis.
4. It is directed along the positive \({z \text-}\)axis.
Subtopic:  Acceleration |
 72%
Level 2: 60%+
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