28. ? The first cannon (the one in First cannon to shoot, but shot lands last. t

Question

28. ? The first cannon (the one in First cannon to shoot, but shot lands last. the back) fires a cannonball at an angle that provides a long range. Soon after, a second nearby cannon (the one in the front) fires a second cannonball at the same initial velocity but at a different angle for a shorter range. The second cannon ball hits the ground first. Both cannonballs hit the ground at the same altitude as the cannon muzzles. Second cannon to shoot, but shot lands first. Which speed vs. time graph below accurately represents the motion of the two cannonballs? (Note that "speed" means the absolute magnitude of the velocity, regardless of direction.) rime C. 0 time time ime 29. The speed vs. time graphs in the previous problem show the shaded areas between the positive velocity lines and the "zero" lines. What must be true of each shaded area? a. The area is greater for the first cannonball's motion. b. The area is greater for the second cannonball's motion. c. Both areas are the same.

Explanation / Answer

28) Starting speeds of both cannonballs are same. Options a and c are ruled out , as starting speeds of two, shown here are different.

Speed vs time graph of a particle is straight line, if accelertaion component in the line of velocity is constant. For projectile thrown at angle other than 90 deg. , angle of velocity with horizontal keeps changing. As a result component of gravitational acceleration in the line of velocity keeps changing. So speed vs time graph can not be straight line.

Hence option d is correct.

29) This area represents , distance travelled by cannonball.

As Cannonball one travels more horizontal distance and is also in air for longer time, area is greater for first cannonball

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