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Some kids are playing by rolling a skateboard across level ground beside a 0.75 m high wall. The goal is to drop from the wall vertically downward onto the skateboard as it passes by. A 45 kg kid manages to land on the 4.5 kg skateboard as it is passing by at 8 m/s, and they move off together horizontally. If the kid is able to stay on, what will be the speed of the kid and skateboard together

Answer :

Answer:

The speed of the kid and the skateboard together is 0.723 m/s

Explanation:

Let the mass of the kid be [tex]m_{k} = 45 kg[/tex]

Let the mass of the skateboard be [tex]m_{s} = 4,5 kg[/tex]

The initial speed of the skateboard, [tex]v_{s} = 8 m/s[/tex]

The initial horizontal speed of the boy as he jumps on the skateboard, [tex]v_{k} = 0 m/s[/tex]

Let the speed of the kid and the skateboard together be v

According to the principle of conservation of momentum:

[tex]m_{k} v_{k} + m_{s} v_{s} = (m_{k} + m_{s}) v[/tex]

Substituting the appropriate values into  the given equation

[tex](45*0) + (4.5*8) = (45 + 4.8) v[/tex]

36 = 49.8 v

v = 36/49.8

v = 0.723 m/s

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