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16 Cards in this Set
- Front
- Back
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A car driven 100 km uses how much energy?
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80kWh
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Energy in a car goes to what 4 main places?
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1. Speeding up and slowing down with brakes.
2. Air resistance 3. Rolling resistance 4. Heat - 75% of energy |
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What kind of energy is acceleration?
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Kinetic
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When a car travels half the speed, what is power consumption?
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Power consumption is 8x's smaller.
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When is the energy dissipation of a car dominated by the brakes?
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If the mass of the car > mass of the tube of air --> mc>pAd
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What is the distance when "city-driving" is dominated by kinetic energy and braking?
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Distance between stop signs is <750 m
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How can you save energy lost to your brakes?
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1. reduce mass of car
2. regenerative brakes 3. drive slower |
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How can you save energy lost to wind resistance?
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1. reduce car's drag coefficient
2. reduce cross sectional area 3. drive slower |
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How efficient are petrol engines?
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25% --> energy lost to engine and radiator heat
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How much energy is used by a car driving 70 mph(110 kmh) for one hour?
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80 kWh
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How much energy is used by a car going 35 mph (55 kmh) for 2 hours?
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20 kWh --> 1/4 the energy for half the speed
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How efficient are electric motors?
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90%
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How much energy do cyclist consume?
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2.4 kWh/ 100 km --> 3% of the energy/km of a car
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What is the coefficient of rolling resistance (Crr) for a car?
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approx. .01
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How much power is needed to overcome rolling resistance for a one ton vehicle?
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3100 W
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How much power goes into the engine of a car with 25% efficiency?
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12 kW
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