Question

If an object is dropped, how fast will it be moving after `4s`?

Answer 1

`39.2m/s`

Explanation:

If an object is dropped, the major force acting on it is gravity. We mostly ignore smaller variables like air resistance. The acceleration of gravity downwards is about `9.8ms^-2`.

Acceleration is how much velocity (`m/s`) changes by the second, so the units for acceleration are `(m/s)/s` or `m/s^2`, which is also written mathematically as `ms^-2`.

If we have four seconds of movement, then multiply that by the acceleration and it will give you the velocity.

`9.8m/s^2 * 4s = 39.2(m*s)/s^2 = 39.2m/s`