Physics A ball is dropped from the roof of a building. the ball strikes the grou
ID: 1421563 • Letter: P
Question
Physics
A ball is dropped from the roof of a building. the ball strikes the ground after 6 s. a) How tall, in meters, is the budding? b) What the magnitude of the ball's velocity just before it reaches the ground? 3. A student throws a ball vertically downward from the top of a building. the ball leaves the thrower's hand with a speed of 10m/s. a) What is its speed after falling for Is? 2 s? 3 s? b) How far does it fall in 1 s? 2 s? 3 s? c) What is the magnitude of its velocity after falling 10 m? 4. A hall is thrown straight up in the air. What is its acceleration at the instant it reaches its highest point? Does the acceleration due to gravity change either in magnitude or in direction, when the velocity of the ball changes direction? Ignore air resistance. 5. What are some examples of falling objects, in which it would be unreasonable to neglect air resistance?Explanation / Answer
2 )
part a ) = s = 1/2*gt^2
s = 4.9 * 36 = 176.4 m
part b )
v = u +gt
v = 9.9*6 = 58.8 m/s
3 )
part a )
v = u + gt
v = 10 + 9.8 = 19.8 m/s
v = 10 + 9.8*2 = 29.6 m/s
v = 10 + 9.8*3 = 39.4 m/s
part b )
s = vt + 1/2*gt^2
s = 10 + 4.9 = 14.9 m
s = 10*2 + 4.9*4 = 39.6 m
s = 10*3 + 4.9 * 9 = 74.1 m
part c )
here velocity is only in vertical direction
v^2 = u^2 + 2gs
v^2 = 10^2 + 2*9.8*10
v = 17.2 m/s
4 )
only gravitaion acceleration g ( 9.8 m/s^2 ) work at that instant .
it never change its direction and magnitude because horizontal component of velocity remain constant so there no acceleration in horizontal side .
5 )
Consider the fall of feather and a massive object from the tall building. It is obvious that the object would reach the ground earlier as compared to the feather. This is because the effect of air resistance on the feather is large relative to that on object. Therefore one cannot neglect the effect of air resistance in such situations.