1. Where can I find a good complete set of Physics lesson plans for a high school teacher who teaches 12th grade Physics students? Are they available for free online. If so, please provide the URLs
2. Please explain the quadratic formula.
Water flows over a waterfall of height 75 m at a volume flow rate of 6.0 m3s-1 and then lands in a pool below.
Outline the energy changes taking place. (1 mark)
In the sport of Bungee Jumping people stand on a high platform and allow themselves to fall while tied to the platform by an elastic cord attached to their ankles. Johanna does a bungee jump (click to see the diagram and the table). The shows three important positions during her motion. In her initial drop, the lowest point she reaches is with her feet 45.0 m below the platform (see diagram above).
As Johanna drops, describe the energy changes taking place. Do this by completing the table in the diagram above by writing increasing, decreasing or constant under the headings gravitational potential energy, kinetic energy and elastic potential energy.
The top row refers to energy changes between her initial position on the platform and position A - the point where the bungee cord just starts to stretch; the middle row as she falls from A to position B, the final equilibrium position; and the bottomw row as she falls from B to position C, the lowest point of her initial drop.
Take Johanna's centre of mass to be about 1 m above her feet when she is standing and her mass to be 54.0 kg. Assume the bungee cord has an elastic constant of 75.0 Nm-1.
Estimate Johanna's vertical speed at point A, the point where the bungee cord just starts to stretch. (3 marks)
A gun fires a 20.0 kg bullet and gives it a horizontal velocity of 400 ms-1. The bullet hits a 3.98 kg mass which is hanging on a string. The length from the ceiling to the centre of the mass is 1.00 m, as shown in the diagram.
After the impact, the bullet remains inside the mass. Calculate the maximum height through which the hanging mass is raised due to the impact. (4 marks)
It is suggested that installing a turbine at the bottom of the waterfall could provide a source of electrical energy. Estimate the power that might be available, stating one assumption that you make. The density of water = 1000 kgm-3. (4 marks)
In fact, not much useful electical energy would be available from such a system because most of the energy simply raises the temperature of the water. Given the following information, calculate the temperature rise for the water.
75% of the potential energy is converted into internal energy.
Specific heat capacity of water = 4200 Jkg-1K-1. (4 marks)
The top of the box for kinetic energy is filled in as an example above. (5 marks)
Calculate the resultant force acting on Johanna when she is at C, the lowest point of her drop. (3 marks)
After reaching the lowest point, the stretched bungee cord accelerates Johanna upwards. In this way she 'bounces' up and down a few times before stopping, hanging by her ankles at the end of the cord.
By how much has the cord stretched when she is in this final position? (2 marks)
