please help!! two solid mechanics problem relating stress, gears etc.

嗨

i am having problems solving two solid mechanics problems... can anyone please help??? the problems are:

问题4:

A 2380 Nm torque is applied to gear D due to input torque from the motor at A, as shown in figure 4. Shafts 1 and 2 are both solid steel, 44 mm in diameter and 600 mm long. Gear B has a diameter of 250 mm and gear C has a diameter of 350 mm. The shear modulus G for steel is 80GN/m^2

Find out:

(a)the maximum stress in shaft 2

(b)the maximum stress in shaft 1

(c)the rotation angle of gear D relative to the motor at A, due to the loading.

Question 5:

The component shown on figure 5 is rigidly attached to a foundation. The cross section of the component is rectangular. A 5kN concentrated force is applied to the top surface of the component in the direction shown. Find out the stresses acting on the surface at position A and show them on an infinitesimal.

i solved all the other problems...but i am stuck with this 2. can anyone please help!!! i am totaly blind about this topic.... couldn't produce a single equation. please help!!