EXAM · VECTORS AND PROJECTILE MOTION

POSITION AND SPEED MID FLIGHT

A projectile is launched from the origin at 45 m/s and 37° above horizontal. Find the total time of flight, the position (x, y) of the projectile at exactly half the flight time, the vertical velocity at that moment, and the speed at that moment. Explain what is physically special about the mid-flight instant.

§ 01

Step-by-step solution

Work through one named subgoal at a time. Each step is checked deterministically against the canonical solver — no AI required to verify correctness. Get an AI explanation when you're stuck.

Step 1

Find the horizontal component of the initial velocity.

Hint

vₓ = v₀·cos(θ). It stays constant for the whole flight.

Step 2

Find the total time of flight.

Step 3

Find the x-coordinate of the projectile at t = T/2.

Step 4

Find the y-coordinate of the projectile at t = T/2.

Step 5

What is the speed of the projectile at t = T/2?

Solution walkthrough
Decompose the launch: vₓ = 45·cos(37°) ≈ 35.93 m/s, vy₀ = 45·sin(37°) ≈ 27.08 m/s. The total time of flight is T = 2·vy₀/g = 2·27.08/9.807 ≈ 5.52 s. At t_mid = T/2 ≈ 2.76 s the horizontal position is x_mid = vₓ·t_mid ≈ 35.93·2.76 ≈ 99.2 m. The vertical position is y_mid = vy₀·t_mid - ½·g·t_mid² ≈ 27.08·2.76 - ½·9.807·2.76² ≈ 74.74 - 37.36 ≈ 37.4 m. The vertical velocity at this moment is vy(t_mid) = vy₀ - g·t_mid = 27.08 - 9.807·2.76 ≈ 0. It is exactly zero — the ball has reached its peak. This is not a coincidence: the ball rises for exactly half the flight time and falls for the other half, by the symmetry of the parabola. At the peak the velocity is entirely horizontal: speed_mid = vₓ ≈ 35.93 m/s. This is also the minimum speed during the flight — the ball is moving slowest at the top. After the peak, vy rebuilds in the downward direction, so the speed increases again until landing. The y-coordinate at mid-flight equals the peak height: H = vy₀²/(2g) ≈ 27.08²/19.614 ≈ 37.4 m, confirming that mid-flight in time and maximum height are the same event.
§ 02

Try it with AI

Continue the conversation with the Physics tutor — the problem context is pre-loaded.

Open in Physics.Ask