If the force \(7\hat i+3\hat j-5\hat k\) acts on a particle whose position vector is \(\hat i - \hat j+\hat k,\) the torque of the force about the origin is?
1. \(2\hat i +12\hat j+10\hat k\)
2. zero
3. \(2\hat i -12\hat j-10\hat k\)
4. \(2\hat i +12\hat j-10\hat k\)

Moment of a couple:

A metal bar \(70\) cm long and \(4.00\) kg in mass supported on two knife edges placed \(10\) cm from each end. A \(6.00\) kg load is suspended at \(30\) cm from one end as shown in the figure. The reactions \(R_1~\text{and}~R_2\) at the knife-edges are: (Assume the bar to be of uniform cross-section and homogeneous.)

1. \(43.12~\text{N}~\text{and}~54.88~\text{N}\)
2. \(54.88~\text{N}~\text{and}~4.312~\text{N}\)
3. \(54.88~\text{N}~\text{and}~43.12~\text{N}\)
4. \(43.12~\text{N}~\text{and}~5.488~\text{N}\)

A \(3~\text{m}\) long ladder weighing \(20~\text{kg}\) leans on a frictionless wall. Its feet rest on the floor \(1~\text{m}\) from the wall as shown in the figure. The reaction forces of the wall and the floor respectively are: