Physics Answers

a boy of mass 60 kg and his sister of mass 49kg play on a seesaw pivoted at its center. if the boy is 2.7 cm away from the pivot. calculate the distance from the other side of the pivot to make the seesaw balaced

1. Determine the discharge over an uncontracted horizontal weir that is 1.5 m high and 4.5 m long. The upstream depth is 2.2 m. Determine the Ink height if the same discharge was desired without exceeding an upstream depth of 1.8 m?

2. Determine the discharge over a standard contracted weir when the upstream water depth is 2.1 m. The weir (one end contraction) is 1.8 m high and has a 1.8 m overflow length. Also determine the approach velocity head in the 4-m-wide channel. Is it significant?

1. A 10-cm ASME flow nozzle is installed in a 20-cm (horizontal) waterline. The attached manometer contains mercury (SG = 13.6) and water and registers a pressure difference of 42-cm. Calculate the discharge in the pipe.

2. Determine the discharge over an uncontracted horizontal weir when the upstream water depth is 7.0 ft. The sharp-crested weir is 9.0 ft long and 6.0 ft high.

1. The maximum flow rate in an 8-in. diameter (horizontal) waterline is 4.3 cfs. If a 4-in. Venturi meter is installed in the pipe to measure flow, estimate the necessary length of a vertical U-tube scale for the differential water-mercury (SG = 13.6) manometer.

2. A 50-cm diameter (horizontal) pipe contains a 20-cm Venturi meter. Determine the flow rate if the pressure difference reading between the throat and entry section in a water-mercury (SG = 13.6) manometer is 1.46 m.

6-36. Reconsider the helicopter in Prob. 6-35, except that it is hovering on top of a 2200-m-high mountain where the air density is 0.987 kg/m3. Noting that the unloaded helicopter blades must rotate at 550 rpm to hover at sea level, determine the blade rotational velocity to hover at the higher altitude. Also determine the percent increase in the required power input to hover at 2200 m altitude relative to that at sea level. Answers. 601 rpm, 9.3 percent

6-38 Water flowing in a horizontal 25-cm-diameter pipe at 8 m/s and 300 kPa gage enters a 90° bend reducing section, which connects to a 15-cm-diameter vertical pipe. The inlet of the bend is 50 cm above the exit. Neglecting any frictional and gravitational effects, determine the net resultant force exerted on the reducer by the water. Take the momentum-flux correction factor to be 1.04.

1. Water enters a 7-cm-diameter pipe steadily with a uniform velocity of 2 m/s and exits with the turbulent flow velocity distribution given by u = umax (I - r/R)1/7. If the pressure drop along the pipe is 10 kPa. determine the drag force exerted on the pipe by water flow.

2. A 5-cm-diameter horizontal jet of water with a velocity of 30 m/s relative to the ground strikes a flat plate that is moving in the same direction as the jet at a velocity of 20 m/s. The water splatters in all directions in the plane of the plate. How much force does the water steam exert on the plate?

a particle in a central force field discribed by the spiral orbit r=r0e^(theta). how to show that the force law is inverse cube and that (theta) veries logrithmically with t?.

1. A 2.5-cm-diameter horizontal water jet with a speed of Vj = 40 m/s relative to the ground is deflected by a 60° stationary cone whose bat diameter is 25 cm. Water velocity along the cone varies linearly from zero at the cone surface to the incoming jet speed of 40 m/s at the free surface.

2. A horizontal war jet impinges against a vertical flat plate at 30 ft/s and splashes off the sides in the vertical plane. If a horizontal force of 500 lbf is required to hold the plate against the water stream. determine the volume flow rate of the water.

1. The large water truck releaser water at the rate of 2400 liters/min through the 80-mm-diameter pipe. if the depth of the water in the truck is 1.5 m, determine the frictional force the road has to exert on the tires to prevent the truck from rolling.

2. The 80-kg man stands on the scale. If the bucket of water has a mass of 10 kg, and water is flowing into it at 0.001 m3/s from a 20-mm-diameter hose, determine the reading on the scale at this instant. Assume the bucket is large so that the rate at which the level of water in the bucket is rising can be neglected.

1. The lawn sprinkler consists of four arms that rotate in the horizontal plane. The diameter of each nozzle is 8 mm and the water is supplied through the hose at 0.006 m3/s and is ejected through the four nozzles into the atmosphere. Determine the torque required to keep the arms from rotating.

2. Water is discharged into the atmosphere from the pipe at 10 m/s. Determine the horizontal and vertical components of force and the moment that is developed at the fixed support A in order to hold the pipe in equilibrium. Neglect the resistance provided by the pipe at C, and the weight of the pipe and the water within it.