In a science lab, a teacher instructed students to attach a piece of very fine steel wool to a clamp stand inside a fume hood. The students then lit a burner placed under the steel wool. The metal strands began to glow bright red and flames filled the steel wool. After the burner was turned off, the metal continued to burn, leaving behind reddish-brown strands that collapsed into a powder when it was touched after cooling. Based on these observations, did the steel wool undergo a chemical change or a physical change? Explain your answer.

When the velocity of an object is doubled, by what factor is its momentum changed? by what factor is its kinetic energy changed? a) the momentum is zero. b) the momentum is not zero. c) difficult to say.

What is the role of the ocular lens?

•• al and bert are jogging side-by-side on a trail in the woods at a speed of 0.75 m/s. suddenly al sees the end of the trail 35 m ahead and decides to speed up to reach it. he accelerates at a constant rate of 0.50 m/s2, while bert continues on at a constant speed. (a) how long does it take al to reach the end of the trail? (b) once he reaches the end of the trail, he immediately turns around and heads back along the trail with a constant speed of 0.85 m/s. how long does it take him to meet up with bert? (c) how far are they from the end of the trail when they meet?