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Answer 1

Question :

Give the correct representation for the position with respect to time of a ball which hits downwards with an initial speed of 900 ft/s at an initial height of 150 ft.

Solution :

Here, the ball initially is at a height of 150 ft.

It is moving downwards with a speed of 900ft/s.

The first thing to notice here is that the height is too less.

For simplicity, assume that the ball is moving straight downwards with a constant speed of 900 ft/s

So it should take less than ⅙th of a second to reach the ground. ( <<< )

It's basically a position time graph for a free falling object.

Initial Velocity = 900 ft/s

Height = 150 ft

According to third equation of motion

v² - u² = 2as

v is 0

>> 0 - 810000 = 300a

>> a = 2700 ft/s² ( It's negative cause downward direction, and including g)

h = ½(a)t²

>> 150 = ½(2700)t²

>> t² = (300/2700)

>> t ≈ 1/3 s approximately

For a position time graph, we are taking the position along the y axis and time along the x axis.

The graph is in the attachment

Additional Information - Check out the velocity time graph too( in the attachment)

• Slope of position time graph is velocity .

• Slope of velocity time graph is acceleration.

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Answer 2

Question,

Give the correct option for the position with respect to time of a ball hits downward with an in a speed of 900 ft/s at an initial height of 150 ft?

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Initial Velocity = 900ft/s

Height = 150ft

The third equation of motion.

= v² - u² = 2as

v is 0

>> 0-810000 = 300a

>> a = 2700ft/s²

H = ½ (a) t²

>> 150 = ½ ( 2700 ) t²

>> t² = ( 300/2700 )

t ≈ ⅓ approximately.