Question

toy giraffe was thrown horizontally from the edge of the table at a velocity of 7.5 m/s. if the table is 1.25 m high. what is the toys velocity just before it hits the ground

Answer 1

Let's first find the time that the toy giraffe takes to reach the ground:

$$y=\dfrac{1}{2}gt^2,$$ $$t=\sqrt{\dfrac{2y}{g}}=\sqrt{\dfrac{2\cdot 1.25\ m}{9.8\ \dfrac{m}{s^2}}}=0.505\ s.$$

Then, we can find the $y$-component of the toy's velocity (the $x$-component of the toy's velocity remains unchainged during the flight of the giraffe):

$$v_y=-gt=-9.8\ \dfrac{m}{s^2}\cdot 0.505\ s=-4.95\ \dfrac{m}{s}.$$

The sign minus means that the vertical component of the toy's velocity directed downward.

Finally, we can calculate the toy's velocity just before it hits the ground:

$$v=\sqrt{v_x^2+v_y^2}=\sqrt{(7.5\ \dfrac{m}{s})^2+(-4.95\ \dfrac{m}{s})^2}=8.98\ \dfrac{m}{s}.$$

Answer:

$v=8.98\ \dfrac{m}{s}.$