Energy is conventionally measured in Calories as well as in joules. One Calorie in nutrition is one kilocalorie, defined as 1 kcal = 4 186 J.
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Chapter 8 Solutions
EBK PHYSICS FOR SCIENTISTS AND ENGINEER
- Under normal conditions the human heart converts about 13.2 J of chemical energy per second into 1.32 W of mechanical power as it pumps blood throughout the body. HINT (a) Determine the number of Calories required to power the heart for one day, given that 1 Calorie equals 4186 J. Cal (b) Metabolizing 1 kg of fat can release about 9000 Calories of energy. What mass of metabolized fat (in kg) would power the heart for one day? kgarrow_forwardAn athlete jumps over a barrier with an initial speed of 2.2 m/s. How much will the athlete be raised during the jump?arrow_forwardYou are driving to work at 60 mph and need to accelerate to 75 mph. How long will it take to reach this speed? Express this quantity in units of seconds. Assume the engine is rated at 140 hp and is 25% efficient. The combined vehicle and driver mass is 2970 lbm.arrow_forward
- A race car with a mass of 1850 kg accelerates from rest down a race track at a rate of 21.0 m/s2. If the track is 400m long, what is the gain in kinetic energy of the car when it reaches the end of the track?arrow_forwardWhat is the kinetic energy of 1 kg of air (about 1 m3) moving at 15 m/s (about 32 mph)? If it takes 2 seconds to raise an 8 kg block a vertical height of 1 m, what is the power expended?arrow_forwardUnder normal conditions the human heart converts about 13.5 J of chemical energy per second into 1.35 W of mechanical power as it pumps blood throughout the body. (a) Determine the number of Calories required to power the heart for one day, given that 1 Calorie equals 4186 J. ______________ Cal (b) Metabolizing 1 kg of fat can release about 9000 Calories of energy. What mass of metabolized fat (in kg) would power the heart for one day? ________________kgarrow_forward
- A typical human brain has a mass of 1.4 kg, which makes up about 2% of a person's mass. However, the brain requires 20% of the body's power consumption. In essence, the brain requires 10 times as much power as any other organ in the body. The average power output of the human brain is about 2.0*10^1 W. Assume that the brain's power output could be converted into mechanical work and calculate how high we could use this power to lift an apple (m=0.20kg) in one minute.arrow_forwardEnergy is conventionally measured in Calories as well as in joules. One Calorie in nutrition is one kilocalorie, defined as 1 kcal = 4 186 J. Metabolizing 1 g of fat can release 9.00 kcal. A student decides to try to lose weight by exercising. He plans to run up and down the stairs in a football stadium as fast as he can and as many times as necessary. To evaluate the program, suppose he runs up a flight of 80 steps, each 0.150 m high, in 65.0 s. For simplicity, ignore the energy he uses in coming down (which is small). Assume a typical efficiency for human muscles is 20.0%. This statement means that when your body converts 100 J from metabolizing fat, 20 J goes into doing mechanical work (here, climbing stairs). The remainder goes into extra internal energy. Assume the student’s mass is 75.0 kg. (a) How many times must the student run the flight of stairs to lose 1.00 kg of fat? (b) What is his average power output, in watts and in horsepower, as he runs up the stairs? (c) Is this…arrow_forwardA 50.0 kg cheetah accelerates from rest to its top speed of 30.3 m/s. (a) How much net work (in J) is required for the cheetah to reach its top speed? (b) One food Calorie equals 4186 J. How many Calories of net work are required for the cheetah to reach its top speed? Note: Due to inefficiencies in converting chemical energy to mechanical energy, the amount calculated here is only a fraction of the energy that must be produced by the cheetah's body.arrow_forward
- While at a water park, Hunter tries the water slide. The starting point is 13.0 m above the ground. He pushes off with an initial speed of 2.5 m/s. If the slide is frictionless, how fast will Hunter be traveling at the bottom?arrow_forwardA typical human brain has a mass of 1.4 kg, which makes up about 2% of a person's mass. However, the brain requires 20% of the body's power consumption. In essence, the brain requires 10 times as much power as any other organ in the body. The average power output of the human brain is about 2.0 × 10¹ W. Assume that the brain's power output could be converted into mechanical work and calculate how high we could use this power to lift an apple (m = 0.20 kg) in one minute. Number pa Unitsarrow_forwardA small block moves at point A with a speed of 6 m/s. Its path is without friction until it reaches the section of length L= 8.6 m where the coefficient of friction is 0.65. The indicated heights are h1 = 5.8m,h2 = 1.8 m. What is the speed of the block at point D? ( Take g = 10 m/s, write the answer with 2 decimal places only).arrow_forward
- Principles of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning