PE = mass * height * 9.81
PE = 142 * 25 * 9.81
PE = 34825.5 J
Answer:
v = 87.57 m/s
Explanation:
Given,
The initial velocity of the car, u = 0
The final velocity of the car, v = 60 mi/hr
The time period of car, t = 8 s
= 0.00222 hr
The acceleration of the car is given by the formula,
a = (v -u) / t
= 60 / 0.00222
= 27027 mi/hr²
If the car has initial velocity, u = 50 mi/hr
The time period of the car, t = 5.0 s
= 0.00139 hr
Using first equations of motion
<em> v = u + at</em>
= 50 + (0.00139 x 27027)
= 87.57 mi/hr
Hence, the final velocity of the car, v = 87.57 mi/hr
Answer: C
high; large
Explanation:
The wave energy is related to its amplitude and frequency.
The wave energy is proportional to the amplitude of the wave. So, wave with the most energy will have high amplitude.
Also, frequency is related to wave energy. The larger the frequency, the more the energy of the wave.
Therefore, The waves with the MOST energy have high amplitudes and large
frequencies.
At critical temperature, the resistivity of the superconductor
B. It suddenly drops to zero
Explanation:
Materials can be classified into three different types depending on their resistance:
- Conductors: these materials have generally low resistance and allow electricity to pass through easily. The resistance of a conductor increases linearly with the temperature
- Insulators: these materials do not allow electricity to pass through - so they have very high resistance
- Semi-conductors: these are materials that are insulators are room temperature, however they becomes conductors when heated. Therefore, the resistance of a semiconductor decreases when the temperature increases
- Superconductors: these are special materials that are normally conductors; however, at very low temperatures (we are talking about temperature very near to 0 K), their resistance becomes suddenly zero.
Therefore, the correct answer is:
B. It suddenly drops to zero
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