WAEC SSCE - Physics - 1997 (Objective)

Question 1 Report

An object falls freely from a height of 25m onto the roof a building 5m high. Calculate the velocity with which the object strikes the roof (g=10$ms^{-2}$

17.3$ms^{-2}$

20$ms^{-2}$ Correct answer

24.5$ms^{-2}$

125$ms^{-2}$

200$ms^{-2}$

Answer Details

To solve this problem, we can use the formula for the final velocity of an object undergoing free fall: v^2 = u^2 + 2gh Where v is the final velocity, u is the initial velocity (which is zero for an object dropped from rest), g is the acceleration due to gravity (given as 10 m/s^2), and h is the height from which the object is dropped. In this case, the object is dropped from a height of 25m, so h = 25m. It falls until it reaches the roof of the building, which is 5m high. So the distance it falls is 25 - 5 = 20m. Substituting these values into the formula, we get: v^2 = 0 + 2 * 10 * 20 v^2 = 400 v = sqrt(400) v = 20 m/s Therefore, the velocity with which the object strikes the roof is 20 m/s. So, the correct option is (b) 20$ms^{-2}$.






Press & Hold to Drag Around
Click Here to Close