A student is standing on a skateboard that is not moving. The total mass of the student and the skateboard is 50 kilograms. The student throws a ball with a mass of 2 kilograms forward at 5 m/s. Assuming the skateboard wheels are frictionless, how will the student and the skateboard move?
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OPTIONS:
- forward at 0.4 m/s
- forward at 5 m/s
- backward at 0.2 m/s
- backward at 5 m/s

backward at 5 m/s

The source of energy for the Earth's water cycle is the
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OPTIONS:
- wind
- Sun's radiation
- Earth's radiation
- Sun's gravity

Sun's radiation

An Italian scientist named Alessandro Volta invented the Voltaic pile in 1800. It was able to produce a steady electrical current. Based on this description, what is the modern equivalent of the Voltaic pile?
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OPTIONS:
- a wire
- a battery
- a resistor
- a light bulb


a battery