Calculate the required compressive strength for a concrete – Civil Engineering

1.A bucket full of water is to be rotated in the vertical plane. What minimum angular velocity, in rad/s, is necessary to keep the water inside if the rotating arm is 120 cm?

2.In a heat exchanger a pipeof outer diameter =60m and inner dia=52.5m with k=0.054kw/m0c is used to heat water.the inside and outside heat transfer coefficients are 1.960kw/m2oc and 0.0079kw/m2oc respestively.estimate the overall heat transfer coefficient?

3.Calculate the required compressive strength for a concrete mix design if F’c = 5000 psi and data indicate a standard deviation of 600 psi based on 15 tests for a similar concrete mix