The ratio of relative strengths of the gravitational force and the electromagnetic force between two charged particles is

The efficiency of an engine is given by $\eta=\frac{\alpha \beta}{\sin \theta} \cdot \log _e \frac{\beta x}{k T}$, where $\alpha$ and $\beta$ are constants. If $T$ is the absolute temperature, $k$ is Boltzmann constant, $\theta$ is angular displacement and $x$ is distance, then the incorrect statement is

A bird flies with a velocity $(t-2) \mathrm{ms}^{-1}$ along a straight line, where $t$ is the time in seconds. The distance covered by it in a time of 4 seconds is

A car is travelling with linear velocity $v$ on a circular road of radius $r$. If its velocity is increasing at a rate of $a \mathrm{~ms}^{-2}$, then the resultant acceleration will be