# Lab 5 Projectile Motion Eleanor Roosevelt High School

Lab 5 Projectile Motion Eleanor Roosevelt High School Mr. Chin-Sung Lin

Calculation of Projectile Motion q Example: A projectile was fired with initial velocity v 0 horizontally from a cliff d meters above the ground. Calculate the horizontal range R of the projectile. v 0 d g t R

Strategies of Solving Projectile Problems q H & V motions can be calculated independently q H & V kinematics equations share the same variable t v 0 d g t R

Strategies of Solving Projectile Problems H motion: dx = v x t R = v 0 t V motion: d y = d = 1 / 2 g t 2 t = sqrt(2 d/g) So, R = v 0 t = v 0 * sqrt(2 d/g) v 0 d g t R

Numerical Example of Projectile Motion H motion: dx = v x t R = v 0 t = 10 t V motion: d y = d = 1 / 2 g t 2 t = sqrt(2 *19. 62/9. 81) = 2 s So, R = v 0 t = v 0 * sqrt(2 d/g) = 10 * 2 = 20 m V 0 = 10 m/s 19. 62 m g = 9. 81 m/s 2 t R

Exercise 1: Projectile Problem A projectile was fired with initial velocity 10 m/s horizontally from a cliff. If the horizontal range of the projectile is 20 m, calculate the height d of the cliff. V 0 = 10 m/s d g = 9. 81 m/s 2 t 20 m

Exercise 1: Projectile Problem H motion: dx = v x t 20 = v 0 t = 10 t V motion: dy = d = 1/2 g t 2 = 1/2 (9. 81) 22 = 19. 62 m So, d = 19. 62 m t=2 s V 0 = 10 m/s d g = 9. 81 m/s 2 t 20 m

Exercise 2: Projectile Problem A projectile was fired horizontally from a cliff 19. 62 m above the ground. If the horizontal range of the projectile is 20 m, calculate the initial velocity v 0 of the projectile. V 0 19. 62 m g = 9. 81 m/s 2 t 20 m

Exercise 2: Projectile Problem H motion: dx = v x t V motion: d y = d = 1 / 2 g t 2 So, 20 = v 0 t = 2 v 0 t = sqrt(2 *19. 62/9. 81) = 2 s v 0 = 20/2 = 10 m/s V 0 19. 62 m g = 9. 81 m/s 2 t 20 m

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