Question

a) make a claim about the friction acting on the skateboarder described by these bar graphs.
b) what evidence can you take from the graph to support your claim?
c) write a response that summarizes your claim and evidence as well as supplying your reasoning for why that claim is correct.

Explanation:

a) Claim: Friction is acting on the skate - boarder as mechanical energy is not conserved.
b) Evidence: The total mechanical energy (sum of potential and kinetic energy) at Time 1 is greater than at Time 2. Since mechanical energy would be conserved in the absence of non - conservative forces like friction, the decrease in mechanical energy indicates friction is present.
c) Reasoning: According to the law of conservation of energy, in an isolated system with only conservative forces (gravity in this case for potential and motion for kinetic), mechanical energy is conserved. But here, the reduction in mechanical energy from Time 1 to Time 2 shows that non - conservative force (friction) is dissipating energy as heat or other forms, which is why the claim that friction is acting on the skate - boarder is correct.

Answer:

a) Friction is acting on the skate - boarder as mechanical energy is decreasing.
b) The total mechanical energy at Time 1 is higher than at Time 2.
c) Mechanical energy is conserved in the absence of non - conservative forces. The decrease in mechanical energy indicates the presence of friction dissipating energy.