In braking an automobile, the friction between the brake drums and brake shoes converts the car's kinetic energy into heat. If a 1500-kg automobile traveling at 30 m/s brakes to a halt, how much does the temperature rise in each of the four 8.0-kg brake drums? (The specific heat of each iron brake drum is 448 J/kg?°C).
What will be an ideal response?
47°C
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Velma, who is moving past you at a high rate of speed, holds a meter stick and a standard kilogram
Is it possible that your measurements could show the standard kilogram to have a mass of 2 kg while the meter stick still has its normal length of 1 m? A) Yes, if Velma holds the meter stick parallel to its direction of motion. B) Yes, if Velma holds the meter stick perpendicular to its direction of motion. C) No, because mass actually decreases with velocity, rather than increasing. D) No; if the kilogram's mass has increased to 2 kg, then it must be longer than 1 m. E) No; if the kilogram's mass has increased to 2 kg, then it must be shorter than 1 m.
For the multiplication of 4.4 m times 1.5 m, the result should be reported with how many significant figures?
a. Two b. One c. Three d. Four e. Seven
Which of the following is a positively charged polyatomic ion?
a. Potassium ion b. Sulfide ion c. Ammonium ion d. Sulfate ion
A woman who normally weighs 400 N stands on top of a very tall ladder so she is one Earth-radius above Earth's surface. What is her weight there?
A) zero B) 100 N C) 200 N D) 400 N E) none of the above