3-8 CHAPTER3-Vectors and Motion in Two Dinensions 37 Projectile Motion: Solving

Question

3-8 CHAPTER3-Vectors and Motion in Two Dinensions 37 Projectile Motion: Solving ProblemsnidowTninoitoM ?.e 38. a. A cart rolling at constant velocity fires a ball straight up. Whenoitom oms sdl siol.no.2? the ball comes down, will it land in front of the launching tube, behind the launching tube, or directly in it? Explain. b. Will your answer change if the cart is accelerating in the forward direction? Ir 39. Four balls are simultaneously launched with the same speed from the same beight h above the ground. At the same instant, ball 5 is released from rest at the same height. Rank in order, from shortest to longest, the amount of time it takes each of these balls to hit the ground. (Some may be simultaneous.) Order Explanation: k in order, from shortest to longest, the amount of time it takes each of these projectiles to hit the ground. (Some may be simaltaneous.) 40. Ran Order Explanation:

Explanation / Answer

Problem 38)

When the ball is in the cart, it is also moving with the same velocity (v) as the cart is.

Now when we fire the ball in the air , it gains a vertical velocity , but there is no force in the horizontal direction to slow the ball. Hence its original velocity in the horizontal i.e. v will be conserved. Hence if it falls back after say time t secs it would have moved (v*t) m in the horizontal direction and the cart would have moved (v*t) m in the horizontal.

So it will land back in the cart.

B)

Yes, it will change because if the cart is accelerating in the forward direction , then when the ball leaves the tube , the horizontal force upon it will disappear. Hence it will move with velocity it had at the time of launch , so if it lands in time t , it will move a horizontal distance of (v*t) m while the cart would have moved v*t + 1/2 *a*t^2 where a = acceleration .

Hence the ball will land behind the tube.

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