Question

A rock is dropped from a tall building. You can ignore air resistance. Determine its final speed and distance traveled after 4 seconds.
(A) speed = 20 m/s, distance = 80 m
(B) speed = 40 m/s, distance = 20 m
(C) speed = 40 m/s, distance = 80 m
(D) speed = 80 m/s, distance = 40 m
(E) speed = 20 m/s, distance = 40 m ​

Answer 1

Answer:

(C) speed = 40 m/s, distance = 80 m

Explanation:

According to Newton law of motion for a falling body:

v = u + gt

Where v is the final velocity, u is the initial velocity, t is the time taken to fall and g is the acceleration due to gravity.

Given that: t = 4 s, g = 10 m/s², u = 0 m/s(at top of building). Therefore substituting values:

v = 0 + 10(4)

v = 40 m/s

To find the distance h, we use the formula:

v² = u² + 2gh

Substituting values:

40² = 0² + 2(10)h

20h = 40² - 0²

20h = 1600

h = 1600 / 20

h = 80 m

The speed = 40 m/s, distance = 80 m