Fig 2.2 shows a support for a leg in plaster and fig 2.3 shows a simplified diagram of the forces acting on the leg . Calculate the force F needed to keep the leg in a horizontal position

In a particular chemical reaction, the energy of the reactants is 30 kj and the energy of the products is 5 kj. 
 the maximum energy of the system is 40 kj. sketch a potential energy diagram for this reaction. make sure to label the energy of the reactants, the energy of the products, the activation energy, and the enthalpy change for the reaction.