Question

A projectile is launched at an angle above the

ground. The horizontal component of the
projectile’s velocity, vx, is initially 40. meters per
second. The vertical component of the projectile’s
velocity, vy, is initially 30. meters per second.
What are the components of the projectile’s
velocity after 2.0 seconds of flight? [Neglect
friction.]
(1) vx = 40. m/s and v
y = 10. m/s
(2) vx = 40. m/s and v
y = 30. m/s
(3) vx = 20. m/s and v
y = 10. m/s
(4) vx = 20. m/s and v
y = 30. m/s

Answer 1

If we neglect friction/air resistance, then the horizontal component
doesn't change, and the vertical component becomes (9.8 m/s downward)
greater each second thanks to gravity.

So, after 2 seconds, the horizontal component is still 40 m/s, and the
vertical component is (30 - 2·9.8) = 10.4 m/s upward.

Choice #1 says this.