7A jib-crane supports a 4 tonne mass from the crane head as shown below. The Samson post is 8 m in length between the derrick and the tie-bar. Attempt EACH

of the following: Explain the terms co-planar and non-coplanar force systems b The magnitude and nature of the force in the derrick arm of the jib-erane c The magnitude and nature of the force in either tie.