A 6.50 ✕ 105 kg subway train is brought to a stop from a speed of 0.500 m/s in 0.500 m by a large spring bumper at the end of its track. What is the force constant k of the spring? N/m

The density of a substance is 4.0 g/cm3. if a sample of the substance has a volume of 25 cm3 then what is the mass

Based on the concept of the wave-like nature of light, huygens' theory of light postulates that the more light was "bent" by a substance the slower it would move while traversing across that substance. a) deflection b) interference c) refraction d) resonance

A100-watt light bulb illuminates a solar cell. the electricity from the solar cell operates a water pump that delivers 1 watt of power. what is the efficiency of the system?