I keep getting 3150 J, considering three sig figs from the data given in the que

Question

I keep getting 3150 J, considering three sig figs from the data given in the question. But I was marked wrong. Can someone break down why that would be? I'm pretty sure it's an error on part of blackboard quiz. (I can't remember the other options, but 3150 was a choice and the most logical one). I want to confirm before I go into the meeting with my prof.

(1/2)mv^2 where v is vcos(theta)

What is the kinetic energy of an ideal projectile of mass 19.2 kg at the apex (highest point) of its trajectory, if it was launched with an initial speed of 26.5 m/s and at an initial angle of 46.9° with respect to the horizontal?

Explanation / Answer

we know that at the highest point in the trajectory velocity in the Y direction is zero but it has a value in the X direction which is calculated by:

Vx = V0 * Cos (theta)
Vx= 26.5 * Cos(46.9)
Vx= 18.10 m/s

Kinetic energy can be calculated with the following formula:
K=1/2 m V^2
K= 1/2 *(19.2)* (18.10)^2

K=3145.056 J ans

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