A car advertisement claims that its 900-kg car accelerated from rest to 30.0 m/s and drove 100 km, gaining 3.00 km in altitude, on 1.0 gal of gasoline. The average force of friction including air resistance was 700 N. Assume all values are known to three significant figures. (a) Calculate the car’s efficiency. (b) What is unreasonable about the result? (c) Which premise is unreasonable, or which premises are inconsistent?

A car advertisement claims that its 900-kg car accelerated from rest to 30.0 m/s and drove 100 km, gaining 3.00 km in altitude, on 1.0 gal of gasoline. The average force of friction including air resistance was 700 N. Assume all values are known to three significant figures. (a) Calculate the car’s efficiency. (b) What is unreasonable about the result? (c) Which premise is unreasonable, or which premises are inconsistent?

Similar questions

If, in actuality, a 750-kg car with an initial speed of 116 km/h is observed to coast up a hill and stops at a height 24.5 m above its starting point, how much thermal energy was generated by friction in J?
(a) What is the efficiency of an out-of-condition professor who does 2.30 ✕ 105 J of useful work while metabolizing 510 kcal of food energy?(b) How many food calories would a well-conditioned athlete metabolize in doing the same work with an efficiency of 25%?
Suppose the car approches a hill and has the intial speed 106 km/h at the bottom of the hill. The driver takes her foot of the gas pedal and allows the car to coast up the hill. if, in actuality, a 740 kg car with an initial speed of 106 km/h is observed to coast up a hill and stops at a height 21 m above above its starting point, how much thermal engery was generate by friction in J?
What is the efficiency of an out-of-condition professor who does 1.90 ✕ 105 J of useful work while metabolizing 510 kcal of food energy? (Enter your answer as a percentage. Enter a number.)% How many food calories (in kcal) would a well-conditioned athlete metabolize in doing the same work with an efficiency of 25%? (Enter a number.)kcal
A car with a mass of m = 980 kg climbs a slope at a constant speed of s = 11.8 m/s and encounters air resistance and friction that totals f = 570 N. The power of the engine is P = 135 kW, but the efficiency is e = 0.37. (In other words, the power delivered to the car is e = 0.37 times the power of the engine.)Write an expression for sin(φ), where φ is the maximum slope angle for which the car can maintain the given speed.Your answer should be in terms of the symbols given in the problem statement and g (the acceleration due to gravity).
When a cyclist expends 1500 W of power to deliver mechanical energy to her bicycle at a rate of 100 W, find the efficiency of her body. Express your answer as a percentage.
An aquarium 3 m long, 6 m wide, and 1 m deep is full of water. Find the work (in J) needed to pump half of the water out of the aquarium. (Use the facts that the density of water is 1000 kg/m3 and gN 9.8.)
A bucket is filled with sand so that the total mass (sand and bucket) is 15 kgs. The bucket is to be lifted to the top of a 30 meter tall building by a rope of negligible weight. However, the bucket has a hole in it, and leaks 0.2 kgs of sand each meter it is lifted. Find the work done lifting the bucket to the top of the building. Joules
(1)An energy-efficient lightbulb, taking in 23.0 W of power, can produce the same level of brightness as a conventional lightbulb operating at power 100 W. The lifetime of the energy-efficient bulb is 10 000 h and its purchase price is $4.00, whereas the conventional bulb has lifetime 750 h and costs $0.46 per bulb. Determine the total savings obtained by using one energy-efficient bulb over its lifetime as opposed to using conventional bulbs over the same time period. Assume an energy cost of $0.20 per kilowatt-hour.$
Energy comes from food and is usually measured in kilocalories [1 kcal = 4.186 kJ]. How many kilocalories of food energy does a person with a metoblic rate of 75.0 W require per day? (Assume 100 percent efficiency.)
A 500 kg dragster reaches a speed of 90 m/s on level ground, starting from rest. Its efficiency is only 8.20% in producing kinetic energy, because of friction and its design for high power without regard to efficiency. (a) How many gallons of fuel does it use during this acceleration, given there are 1.30 x 10 3 of energy per gallon? gal (b) How much waste beat (in 3) is produced? 3 (c) Once it is brought back to rest (assuming the engine shuts off at the end of the race), how much waste heat (in 3) has been produced?
Shoveling snow can be extremely taxing since the arms have such a low efficiency in this activity. Suppose a person shoveling a footpath metabolizes food at the rate of 750 W. (The efficiency of a person shoveling is 3%.) (a) What is her useful power output (in W)? Answer________________ W (b) How long (in s) will it take her to lift 2600 kg of snow 1.20 m? (This could be the amount of heavy snow on 20 m of footpath.) Answer________________ s (c) How much waste heat transfer in kilojoules will she generate in the process? Answer________________ kJ