Select one: a. -12 m/s b. zero c. -175 m/s d. +12 m/s e. +175 m/s Select one: a.

Question

Select one: a. -12 m/s b. zero c. -175 m/s d. +12 m/s e. +175 m/s Select one: a. -12 m/s b. zero c. -175 m/s d. +12 m/s e. +175 m/s a. -12 m/s b. zero c. -175 m/s d. +12 m/s e. +175 m/s A ball is projected upward at time t = 0.0 s, from a point on a roof 10 m above the ground. The ball rises, then falls and strikes the ground. The initial velocity of the ball is Consider all quantities as positive in the upward direction. At time the velocity of the ball is closest to: Select one: -12 m/s zero -175 m/s +12 m/s +175 m/s

Explanation / Answer

As u go up the velocity decreases because the ball is acting against to the gravity but this is considered as positive so the upward velocity is positive and downward velocity is negative and more ever if the ball is comming down it gains velocity. it increases its magnitude and it depends upon the height the ball has reached.

So the options b, d ane e are wrong because the velocities are negative in downward direction.

And the minimum velocity that can the ball can be reached is caluculated as:

v^2 - u^2 =2gh

Let the inital velocity, u = 0 m/s and height, h = 10m

v^2 = 2*9.81*10

v = 14.1 m/s

And if the inital velocity is there then ball will rise some height and from there the ball will fall freely under gravity. So option a is wrong. Therefore, the correct option is c.) -175 m/s

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