A projectile is thrown upward at an angle 60° with the horizontal. The speed of the projectile is 20 m/s when its direction of motion is 45° with the horizontal. The initial speed of the projectile i $s_____$ m/s.
Options

Question

A projectile is thrown upward at an angle 60° with the horizontal. The speed of the projectile is 20 m/s when its direction of motion is 45° with the horizontal. The initial speed of the projectile i $s_____$ m/s.

Options

G1 Physics · Accepted Answer

The horizontal component of projectile velocity remains constant throughout the motion. Let the initial speed be u. Initially, horizontal component = u cos60° = u/2. At the instant when the projectile speed is 20 m/s and its direction is 45° above the horizontal, horizontal component = 20 cos45° = 20/√2 = 10√2 m/s. Therefore, u/2 = 10√2. Hence, u = 20√2 m/s. Correct option: D.

A projectile is thrown upward at an angle 60° with the horizontal. The speed of the projectile is 20 m/s when its direction of motion is 45° with the horizontal. The initial speed of the projectile i s_____ m/s.