A hockey puck slides off the edge of a platform with an initial velocity of 20 m/s horizontally.The height of the platform above the ground is 2.0 m.What is the magnitude of the velocity of the puck just before it touches the ground? You can neglect air resistance.
A)21 m/s
B)22 m/s
C)24 m/s
D)25 m/s
E)6.3 m/s

Question

Quizplus · Accepted Answer

The magnitude of the velocity just before the puck touches the ground can be found using the Pythagorean theorem, combining the horizontal velocity (which remains constant at 20 m/s due to no horizontal forces acting on the puck) and the vertical velocity it gains while falling. The vertical velocity can be found using the equation $v = \sqrt{2gh}$, where $g$ is the acceleration due to gravity (9.8 m/s$^2$) and $h$ is the height (2.0 m). Calculating the vertical velocity gives $v = \sqrt{2 \times 9.8 \times 2} = \sqrt{39.2} \approx 6.26$ m/s. Then, the total velocity just before touching the ground is $\sqrt{20^2 + 6.26^2} \approx 21$ m/s.

A Hockey Puck Slides Off the Edge of a Platform