An engine of mass 200 kg is to be supported on four helical springs. When the engine speed is 1000 rpm there is a primary vertical periodic force of maximum value 350 N due to the unbalanced...

An engine of mass 200 kg is to be supported on four helical springs. When the engine speed is 1000 rpm there is a primary vertical periodic force of maximum value 350 N due to the unbalanced reciprocating weights. Assume that the engine vibrates in the vertical direction with no horizontal or angular movement. (a) Find the sti¤ness of each spring to limit the maximum total periodic force on the foundation to 25 N. (b) What will be the amplitude of vibration of the engine when its speed is 500 rpm?