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16 Cards in this Set

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