1. a) A projectile is fired at 25 deg above the horizontal. It\'s initial speed

Question

1. a) A projectile is fired at 25 deg above the horizontal. It's initial speed is equal to 25 m/s. Assume that the free-fall acceleration is constant throughout and that the effects of the air can be ignored. What's the max height reached by the projectile? * I got this part to be 5.69 m but need part b*

b) At what time after being fired does the projectile reach this max height?

2. A 5.9 kg block on a horizontal frictionless floor's pulled by a cord that exerts a force F=11 N at an angle theta = 33.3 above the horizontal. What's the speed of the block 6.1 seconds after it starts moving?

Explanation / Answer

(A) at maximum height, vertical component of velocity willl become zero .

vfy = 0

initial vertical velcoity = vyi = 25 sin25 = 10.565 m/s

and a = - g = - 9.81 m/s^2

Applying vf = vi + a t

0 = 10.556 - 9.81 t

t = 1.08 sec

2. In horizontal, Fcos(33.3) = m a

11 cos(33.3) = 5.9a

a = 1.56 m/s^2

v = u + a t

v = 0 + (1.56 x 6.1) = 9.51 m/s

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