Question

problem reference 6.2
the 70.0 kg skateboarder in the drawing starts down the left side of the ramp with an initial speed of 4.50 m/s. neglect nonconservative forces, such as friction and air resistance.
what is the initial kinetic energy of the skateboarder, when he starts down the left side of the ramp?
709 j
158 j
0 j
1,420 j

Explanation:

Step1: Recall the formula for kinetic energy

The formula for kinetic energy is \(K = \frac{1}{2}mv^{2}\), where \(m\) is the mass and \(v\) is the velocity.

Step2: Substitute the given values

Given \(m = 70.0\space kg\) and \(v=4.50\space m/s\). Substitute into the formula: \(K=\frac{1}{2}\times70.0\times(4.50)^{2}\).
First, calculate \((4.50)^{2}=20.25\). Then \(\frac{1}{2}\times70.0 = 35.0\).
Multiply \(35.0\times20.25 = 708.75\approx709\space J\).

Answer:

709 J