### Home > CALC > Chapter 12 > Lesson 12.2.1 > Problem 12-67

12-67.

A projectile is launched from the ground at a seconds) given by

*. Its horizontal displacement in feet is given by*

.

Find an expression for the velocity vector as a function of

. Calculate the magnitude of the velocity vector at

and at the moment when the projectile hits the ground. Make a conjecture about the speed with which projectiles return to earth.To determine when the projectile hits the ground, solve

.

The velocity vector whenis:

Sketch this vector and use the Pythagorean Theorem to determine its magnitude.