The variable <span><span>xx</span>x</span><span> is often used to represent the horizontal position. The variable y</span> is often used to represent the vertical <span>The airplane passenger’s initial position is </span><span><span>x_0=6.0\text{ m}<span><span>x<span><span>0</span><span></span></span></span>=6.0<span> m</span></span></span>x, start subscript, 0, end subscript, equals, 6, point, 0, space, m</span><span> and his final position is </span><span><span>x_f=2.0\text{ m}<span><span>x<span><span>f</span><span></span></span></span>=2.0<span> m</span></span></span>x, start subscript, f, end subscript, equals, 2, point, 0, space, m</span>, so his displacement can be found as follows,<span>Δx=<span>xf</span>−<span>x0</span>=2.0 m−6.0 m=−4.0 m</span><span>. His displacement is negative because his motion is toward the rear of the plane, or in the negative x direction in our coordinate system.</span>position.
It does produce 'sound' ... a compression wave traveling through the air. But your ears don't hear a sound that's vibrating less than 20 or 30 times every second. If you could swing your pendulum that fast, you could hear the sound of its vibrations pushing the air around.
The statement about "<span>efficiency compared the output work to the output force" is false. Efficiency can be compared from the input work to the output work.</span>
The rock will continue to travel in a straight line with a constant velocity for ever... The reason is, once it leaves your hand there is no force acting on the rock, so it will just continue to move in a natural motion which is constant velocity.