When you rub a match against a rough surface, fire results, giving off light and heat. the law of conservation of energy says that energy cannot be created.

how can you explain the fire seeming to come from nowhere?

the energy was stored in chemical bonds before it became heat and light.
matches are made to take up energy from surfaces.
the energy started out as the sound energy of the rubbing match.

1134567 a jet with mass m = 1.1 ă— 105 kg jet accelerates down the runway for takeoff at 2 m/s2. 1) what is the net horizontal force on the airplane as it accelerates for takeoff? 2.2*10^5 n your submissions: 2.2*10^5 computed value: 220000submitted: saturday, january 26 at 2: 41 pm feedback: correct! 2) what is the net vertical force on the airplane as it accelerates for takeoff? 0 n your submissions: 0 computed value: 0submitted: saturday, january 26 at 2: 41 pm feedback: correct! 3) once off the ground, the plane climbs upward for 20 seconds. during this time, the vertical speed increases from zero to 21 m/s, while the horizontal speed increases from 80 m/s to 95 m/s. what is the net horizontal force on the airplane as it climbs upward? n 4) what is the net vertical force on the airplane as it climbs upward? n 5) after reaching cruising altitude, the plane levels off, keeping the horizontal speed constant, but smoothly reducing the vertical speed to zero, in 13 seconds. what is the net horizontal force on the airplane as it levels off? n 6) what is the net vertical force on the airplane as it levels off?

An incident ray through the focal point of a spherical mirror will: reflect through the center of curvature. reflect back through the focal point. reflect parallel to the principle axis. reflect the same direction as the incident ray.

Consider a system with two masses that are moving away from each other. why will the kinetic energy differ if the frame of reference is a stationary observer or one of the masses?