A 25 kg rock falls for 2.7 seconds. How many meters tall was the building?
1 answer:
Answer:
35.7m
Explanation:
Given parameters:
Mass of rock = 25kg
Time of fall = 2.7s
Unknown:
Height of the building = ?
Solution:
To solve this problem, we will use one of the motion equations;
S = ut + gt²
S is the height
u is the initial velocity = 0m/s
t is the time
g is the acceleration due to gravity
S = (0 x 2.7) + x 9.8 x 2.7² = 35.7m
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Answer:
option (a) 0.61 s
Explanation:
Given;
Time taken by the ball to reach the ground = 0.50 s
Let us first calculate the distance through which the ball falls on the ground
from the Newton's equation of motion, we have
where,
s is the distance
a is the acceleration
t is the time
here it is the case of free fall
thus, a = g = acceleration due to gravity
u = initial speed of the ball = 0
on substituting the values, we get
or
s = 1.225 m
Now,
when the elevator is moving up with speed of 1.0 m/s
the initial speed of the ball = -1.0 m/s (as the elevator is moving in upward direction)
thus , we have
or
or
4.9t^2 - t - 1.225 = 0
or
t = 0.612 s
hence, the correct answer is option (a) 0.61 s