Question

A marble, rolling with speed of 20m/sec rolls off the edge of the table that is 180m high (g=10m/sec2), find time taken to drop to the ground.
a. 10sec
b. 8sec
c. 6sec
d. 12sec​

Answer 1

Answer:

Choice: c. 6sec

Explanation:

Horizontal Launch

When an object is thrown horizontally with a speed (v) from a height (h), it describes a curved path ruled by gravity until it finally hits the ground.

The horizontal component of the velocity is always constant because no acceleration exists in that direction, thus:

$v_x=v$

The vertical component of the velocity changes in time because gravity makes the object fall at increasing speed given by:

$v_y=g.t$

Where $g=10 m/s^2$

To calculate the time the object takes to hit the ground, we use the same formula as for free-fall, since the time does not depend on the initial speed:

$\displaystyle t=\sqrt{\frac{2h}{g}}$

The marble rolls the edge of the table at a height of h=180 m, thus:

$\displaystyle t=\sqrt{\frac{2*180}{10}}$

$\displaystyle t=\sqrt{36}$

t = 6 sec

Choice: c. 6sec

Answer 2

Answer:

The answer is:

C) 6sec

Hope it helps:D