A truck is moving with a constant velocity of `54 km h^-1`. In which direction (angle with the direction of motion of truck) should a stone be projected up with a velocity of `20 ms^-1`, from the floor of the truck of the truck, so as to appear at right angles to the truck, for a person standing on earth ?

Explanation

To solve the problem of determining the angle at which a stone should be projected from a truck moving at a constant velocity, we can follow these steps:

### Step-by-Step Solution:

1. **Convert Truck's Velocity to m/s**:
The truck is moving at a velocity of `54 km/h`. We need to convert this to meters per second (m/s).
\[
\text{Velocity of the truck} = 54 \, \text{km/h} \times \frac{5}{18} = 15 \, \text{m/s}
...