1. An 80-kg quarterback jumps straight up in the air right before throwing a 0.43-kg football horizontally at 15 m/s. How fast will he be moving backward just after releasing the ball?2. Which of the following best describes why you can analyze this event using conservation of momentum?A. The throwing action is quick enough that external forces may be ignored. B. External forces don't act on the system during the jump. C. Conservation of momentum is always the best way to analyze motion.

1) 0.0806 m/s

2) External forces don't act on the system during the jump

Explanation:

velocity of ball ( Vbf )= 15 m/s

mass of quarter back ( Mq )= 80 kg

mass of football ( Mb ) = 0.43 kg

A) How fast will be be moving backward just after releasing the ball

we can determine this speed with the use of conservation of momentum equation

= Mb ( Vbf - Vbi ) = Mq ( Vq )

where Vq = Mb ( Vbf - Vbi ) / Mq

                 = 0.43 ( 15 m/s - 0 ) / 80 kg

                 = 0.0806 m/s

B) External forces don't act on the system during the jump

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.

b.a device that inputs heat into a cool object