Asmall sphere with mass m is attached to a massless rod of length l that is pivoted at the top, forming a simple pendulum.

the pendulum is pulled to one side so that the rod is at an angle θ from the vertical, and released from rest.

(a) in a diagram, show the pendulum just after it is released. draw vectors representing the forces acting on the small sphere and the acceleration of the sphere. accuracy counts! at this point, what is the linear acceleration of the sphere?

(b) repeat part (a) for the instant when the pendulum rod is at an angle θ/2 from the vertical.

(c) repeat part (a) for the instant when the pendulum rod is vertical. at this point, what is the linear speed of the sphere?

Answer: a charge of -1.0  × 10⁻⁴ c must be placed  at x = 26 m.the sign of the charge will be the same sign as the  -4.0  µc charge.======electricstatic force between two point charges  is given by    where k is coulomb's constant,  8.99×10⁹  n·m²/c², q₁ and q₂ are the point charges, and r is the distance between the two point charges.assign positive to q₁let q₁ =  6.0 µc, q₂ = -4.0  µc, q₀ represent the charge at the origin, and q₃ represent this new charge to place.the charge at the origin q₀ would experience the following force f₀₁ from q₁, with r = 6.0 m (note that 1  µc = 10⁻⁶ c)    the force from q₂    the force from q₃    the net force on the origin charge, q₀, has to be zero for no electrostatic forcehaving an equation where k and q₀ can be divided out of the equation will allow us to solve for q₃    isolating:     a charge of -1.0  × 10⁻⁴ c must be placed  at x = 26 m.the sign of the charge will be the same as the  -4.0  µc charge

The cell reaction uses external supplies of a full and an oxidant, which are consumed and needs to be provided continuously. the cell will continue to provide electrical energy so long as there is a supply of fuel and oxidant.  hope this ! (:  

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