Week 11 - Conservation of Mechanical Energy

Question 1

Conservation of Mechanical Energy and equation

Answer 1

Total mechanical energy of an object is constant or conserved when no external forces (other than gravity) act on the object (e.g. projectile motion)

(𝐾𝐸 + 𝑃𝐸)𝑏𝑒𝑓𝑜𝑟𝑒= (𝐾𝐸 + 𝑃𝐸)𝑎𝑓𝑡𝑒𝑟

Question 2

Equation for kinetic energy

Answer 2

KE = 1/2mv²

Question 3

Equation for Potential Energy

Answer 3

PE = mgh

mass x gravity x height

Question 4

A diver standing on the 10 m platform has a mass of 55 kg. Calculate her velocity just before impact with the water.

Using (PE + KE)before = (PE + KE)after

Show all working out

Answer 4

𝑣 = 14.01 𝑚/s

Question 5

If you throw a 500gram ball vertically into the air and it leaves your hand with a velocity of 15m/s, how high will it go?

Answer 5

Height = 11.47m

Question 6

Explain this picture in biomechanical terms

Answer 6

Energy is the capacity to do work - to do 100 J of work, you must expend 100 J of energy

Represents a change in mechanical energy, area under force-time curve = energy

Power is the rate at which work is done

If you do 100 J of work in 1 s (using 100 J of energy), the power is 100 J/s

Question 7

Why is it harder running on sand than a running track?