The length of a 25-m wire increases by 0.25 cm when it is heated from 20°C to 90°C. What is the coefficient of linear expansion of the wire?
a. 1.43 × 10^–6/ºC
b. 1.43 × 10^–4/ºC
c. 8.93 × 10^–4/ºC
d. 8.93 × 10^–2/ºC
a
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Bumpers on cars are not of much use in a collision
To see why, calculate the average force a bumper would have to exert if it brought a 1200-kg car (a so-called compact model) to a rest in 15 cm when the car had an initial speed of 2.0 m/s (about 4.5 mph). (Bumpers are built with springs that compress to provide a stopping force without, hopefully, denting the metal.) A) 1.8 × 104 N B) 1.6 × 104 N C) 5.4 × 104 N D) 6.5 × 105 N E) 3.2 × 104 N
The length of a certain wire is doubled and at the same time its radius is increased by a factor of 4. What is the change in the resistance of this wire?
A) It is reduced by a factor of 8. B) It increases by a factor of 8. C) It is reduced by a factor of 4. D) It increases by a factor of 4. E) It stays the same.
Scientific thinking developed only in the past few decades
Indicate whether the statement is true or false
An object moves at a constant velocity of 12 m/s to the southwest for an interval of 30 s. Halfway through this interval, what is the magnitude of its instantaneous velocity?
a. It can be any value from 0 to 24 m/s. b. 12 m/s c. 6 m/s d. More information is needed. e. 24 m/s