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polet [3.4K]
4 years ago
13

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 v

ertically 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
Physics
1 answer:
lys-0071 [83]4 years ago
7 0

Answer:

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

Explanation:

Let the mass of the kid be m_{k} = 45 kg

Let the mass of the skateboard be m_{s} = 4,5 kg

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

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

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

According to the principle of conservation of momentum:

m_{k} v_{k} + m_{s} v_{s} = (m_{k} + m_{s}) v

Substituting the appropriate values into  the given equation

(45*0) + (4.5*8) = (45 + 4.8) v

36 = 49.8 v

v = 36/49.8

v = 0.723 m/s

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3 years ago
1. 412.9 g of dry ice sublimes at room temperature. a. What’s changing? --- sublimation b. What constant will you use? ----- 25.
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a. The phase (or state of matter) of the substance: from solid state to gas state (sublimation)

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e. The amount of energy being transferred is

Q=m\lambda=(412.9 g)(571 J/g)=2.36\cdot 10^5 J=236 kJ

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a. The phase (or state of matter) of the substance: from gas state to liquid state (condensation)

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e. The amount of energy being transferred is

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3. 3.64 kJ

a. Only the temperature of the substance (which is increasing)

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c. The equation to use will be Q=m C_s \Delta T, where m is the mass of silver, Cs is the specific heat capacity and \Delta T the increase in temperature

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