A body of mass 2.5 kg is placed on a smooth inclined plane with an angle of inclination of 65°. If the initial velocity of the body is 4 m/s, calculate its velocity after 2 seconds.

The mass of the body $m = 2.5 \text{ kg}$.
The angle of inclination $\theta = 65^\circ$.
The initial velocity $u = 4 \text{ m/s}$.
The time $t = 2 \text{ s}$.
The acceleration due to gravity $g = 10 \text{ m/s}^2$.

For a smooth inclined plane, the acceleration $a$ is given by the component of gravity acting along the incline.

Substitute the values:

The final velocity $v$ can be found using the equation:

Substitute the initial velocity, acceleration, and time:

Rounding to one decimal place:

The velocity after 2 seconds is $\boxed{\text{22.1 m/s}}$.