Answer
a) $\Delta U=0.70J$
b) $v_A=1.2m/s$
c) increase
d) stay the same
Work Step by Step
(a) We can find the required change in gravitational potential energy as follows:
$\Delta U=mg\Delta y$
$\implies \Delta U=mgL(1-cos\theta)$
We plug in the known values to obtain:
$\Delta U=(0.33)(9.81)(1.2)(1-cos35^{\circ})$
$\Delta U=0.70J$
(b) We can find the required speed as
$v_A=\sqrt{v_B^2-\frac{2\Delta U}{m}}$
We plug in the known values to obtain:
$v_A=\sqrt{(2.4)^2-\frac{2(0.70)}{0.33}}$
$v_A=1.2m/s$
(c) We know that the change in gravitational energy is directly proportional to the mass. Thus, if the mass of the bob is increased then the answer to part(a) will increase.
(d) We know that if the mass of the bob is increased then the answer to part (b) will stay the same.
