posted by physics .
Initially (at time t = 0) a particle is moving vertically at 5.8 m/s and horizontally at 0 m/s. Its horizontal acceleration is 2.1 m/s2.
At what time will the particle be traveling at 54 with respect to the horizontal? The acceleration due to gravity is 9.8 m/s2.
The question here is what force other than grvity is the particle being subjected to? You stated a horizontal acceleration, but what about vertical? is the vertical acceleration zero?
The vertical acceleration is 9.8 m/s^2 because of gravity. So in the negative y direction.
I think it's saying only gravity is affecting the particle on the y-axis.