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8th Grade Physics Review

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  • If Earth suddenly stopped spinning, would the length of a day become shorter or longer?
    Much longer. One day would last about one year.
  • What force slows the parachutist down?
    Air Resistance
  • Why do high heels create more pressure than sneakers?
    Smaller contact area.
  • A force of 10 N moves an object 3 m. How much work is done?
    30 J
  • Why doesn't the Moon fall onto Earth if gravity is pulling on it all the time?
    The Moon is moving sideways fast enough to stay in orbit around Earth.
  • Imagine there was no friction anywhere on Earth for one day. Name two everyday activities that would become very difficult or impossible.
    Walking, driving, braking, writing, climbing stairs, holding objects, riding a bicycle, etc.
  • Why does the shadow form?
    The object blocks light.
  • Why doesn't the person sink deeply into the snow?
    The large area reduces pressure.
  • Why can't we hear sound in space?
    There is no medium (air) for sound to travel through.
  • What happens when light hits a mirror?
    It reflects.
  • Why is wearing a seatbelt important?
    It stops your bodies inertia from continuing forward during a crash.
  • A battery-powered flashlight is turned on. Put these energy types in order: Chemical Energy Light Energy Electrical Energy
    Chemical → Electrical → Light
  • A bowling ball and a tennis ball are dropped from the same height on the Moon. Which hits the ground first?
    They hit the ground at the same time because there is almost no air resistance on the Moon.
  • What is the SI unit of force?
    Newton (N).
  • Astronauts on the International Space Station are constantly falling toward Earth. Why don't they crash?
    They are moving sideways so fast that they keep missing Earth. This is called an orbit.
  • What would happen first if you fell toward a black hole: A) Freeze B) Burn C) Be stretched like spaghetti
    C – Scientists call it "spaghettification."
  • What is the unit of work?
    Joule (J).
  • Why is the astronaut floating?
    Continuous free fall around Earth.
  • A black car and a white car are parked in the Sun on a hot day. Which one will usually get hotter? Why?
    The black car because dark colors absorb more light energy.
  • What energy is increasing as the cyclist goes downhill?
    Kinetic Energy
  • What force pulls objects toward Earth?
    Gravity.
  • A meteor enters Earth's atmosphere and starts glowing red-hot. Where does the heat energy come from?
    Kinetic energy is converted into heat due to friction and compression of the air.
  • Why use a ramp instead of lifting directly?
    Less force is needed.
  • Why are tractor tires so wide?
    To reduce pressure on the ground.
  • What is mechanical work?
    When a force moves an object.
  • A force of 25 N moves an object 4 m. How much work is done?
    100 J.
  • A rocket is sitting on the launch pad. Does it have kinetic energy, potential energy, both, or neither?
    Potential energy. It is not moving, so it has no kinetic energy yet, but the fuel contains stored chemical energy and the rocket has gravitational potential ene
  • What is friction?
    A force that opposes motion.
  • The Sun produces enormous amounts of energy every second. What type of energy production happens inside the Sun?
    Nuclear fusion.
  • What happens to potential energy when a ball falls?
    It changes into kinetic energy.
  • If gravity suddenly doubled, what would happen to your weight?
    Your weight would double.
  • What is pressure?
    Force acting on an area.
  • What is a force?
    A push or a pull.
  • Name three simple machines.
    Any three: Lever, Pulley, Inclined Plane, Wheel and Axle, Screw, Wedge.
  • What type of energy does an object high above the ground have?
    Potential Energy.
  • What is the speed of light?
    299,792,458 m/s(exact) , 300,000 km/s, or 186,000 miles/s
  • If the Sun suddenly became a black hole of the same mass, what would happen to Earth's orbit?
    Earth would continue orbiting almost exactly the same way. Gravity depends on mass, not whether the object is a star or black hole.
  • Why is a sharp knife easier to use?
    A smaller area creates greater pressure.
  • What type of energy does a moving object have?
    Kinetic Energy.
  • Why doesn't the bird get electrocuted?
    It does not complete an electrical circuit.
  • What simple machine helps lift the load?
    Pulley
  • Why do we see lightning before hearing thunder?
    Light travels faster than sound
  • Why do race cars need special tires?
    To increase friction and grip.
  • What is speed?
    Distance divided by time.
  • A car travels 120 km in 2 hours. What is its speed?
    60 km/h.
  • What is refraction?
    The bending of light when it moves between materials.
  • How does light normally travel?
    In straight lines.
  • Why does the straw look bent?
    Refraction
  • What type of energy is greatest at the top of the roller coaster?
    Potential Energy
  • Which travels faster: sound or light?
    Light.
  • Why do football players wear cleats?
    To increase friction with the ground.
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