Can you please have a look at the attached file.

I am having difficulty with Q6 part (v), not sure how to go about it.

Any help is greatly appreciated.

 

You know Ke, thus

The voltage developed across the motor terminals, without the 5 ohm resistor connected, is

E=Ke*ω

You know Ke and ω thus you can calculate E (which is actually the back EMF when it is working as a motor).

The armature resistance is 5 ohms and the load resistance (connected on the motor terminals) is also 5 ohms. Thus the total resistance is 10 ohms. Thus the current through the armature and the load resistance is :

I=E/10

Thus the power dissipated in the load is:

P=(I^2)*5

Assuming no losses, the torque is:

T=P/ω