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Sergio [31]
2 years ago
10

A ball is thrown straight up with an initial speed of 30 m/s. What is its speed after 4.2 s?

Physics
2 answers:
scZoUnD [109]2 years ago
5 0

11.16 m/s.

Notice I'm not telling you whether that's up or down, because you only asked for the speed, which has no direction.

This would have been a great question to ask for the ball's velocity.

olasank [31]2 years ago
3 0

Answer:

vf = -11.16 m/s

Explanation:

vf = vi + gt

vf = 30 + (-9.8)(4.2)

vf = -11.16 m/s

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First, convert all the km/hr into m/s

You will get that
initial speed = 20 m/s
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relative acceleration = -4 m/s^2

v = u + at
0 = 60 - 4t

t = 15s

s = ut + 1/2  *at * t

s = 60 * 15  - 1/2 *4 * 225
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hope this helps

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3 years ago
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pantera1 [17]

\Large {{ \sf {Question :}}}

<h3>A boy who is riding his bicycle, moves with an initial velocity of 5 m/s. Ten second later, he is moving at 15 m/s. What is his acceleration?</h3>

\Large {{ \sf {Given :}}}

<h3>Initial Velocity (<em>u</em>) - 5 m/s</h3><h3>Final Velocity (<em>v</em>) - 15 m/s</h3><h3>Time (<em>t</em>) - 10 sec</h3>

\Large {{ \sf {Formulae  :}}}

<h3>If the velocity of an object changes from an initial value <em>u </em>to the final value <em>v </em>in time <em>t,</em><em> </em>the acceleration <em>a</em> is, </h3><h3>a \:  =  \frac{v - u}{t}</h3><h3>\Large {{ \sf {Step-by-step explanation :}}}</h3>

a \:  =  \frac{v - u}{t}  \\ or \:  \: a =  \frac{(15 - 5)}{10} m \: s^{ - 2}  \\ or \:  \: a \:  =  \frac{10}{10}m \: s^{ - 2} \\ or \:  \: a = 1m \: s^{ - 2}

\Large {{ \sf {Answer :}}}

<h3>His acceleration is </h3><h3>1m \: s^{ - 2}</h3><h3 /><h3 />
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