Two identical pellet guns are fired simultaneously from the edge of a cliff. The

Question

Two identical pellet guns are fired simultaneously from the edge of a cliff. These guns impart an initial speed of 30 m/s to each pellet. Gun A is fired straight upward, with the pellet going up and then falling back down, eventually hitting the ground beneath the cliff. Gun B is fired straight downward. In the absence of air resistance, how long after pellet B hits the ground does pellet A hit the ground?


The greatest height reported for a jump into an airbag is 99.4 m by stuntman Dan Koto. In 1948 he jumped from rest from the top of the Vegas World Hotel and Casino. He struck the airbag at a speed of 39 m/s (88 mi/h). To assess the effects of air resistance, determine how fast he would have been traveling on impact had air resistance been absent

Explanation / Answer

For the gun that is shot straight upward, think about this: At its highest point, it will have a velocity of 0.(because itis in projectile motion) However, it will need to come backdown eventually. Thus, when it reaches the height of the cliffagain , it will again have a speed of 30m/s downward ( just as theother bullet). Thus we need to find the time it takes for thebullet to go to its highest point and reach the height of the cliffagain. V = 0 highest point ; T = 3.06 sec to go to its highest point. Neglecting air drag , it will take another 3.06 sec to comedown, where it will now have an identical (30 m/s downward)velocity just as the other gun which was shot straight down.Without the "projectile" motion aspect, they are firing down at the same speed at this point. so t = 6.12 seconds

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