Physics Answers

Part 1. The tide gate opens automatically when the tidewater at B subsides, allowing the marsh at A to drain. For the water level h = 4 m, determine the horizontal reaction at the smooth stop C. The gate has a width of 2 m. At what height h will the gate be on the verge of opening?

Part 2. Determine the critical height h of the water level where the concrete gravity darn starts to tip over. The density of concrete is p_c = 240 Mg/m³. Hint: Work the problem using a 1-m width of the dam.

Part 1. Water in the reservoir is used to control the water pressure in the pipe at A. If h = 200 mm, determine this pressure when the mercury is at the elevation shown. Take p_Hg = 13 550 kg/m³. Neglect the diameter of the pipe.

Part 2. The two tanks A and B are connected using a manometer. If waste oil is poured into tank A to a depth of h = 0.6 m, determine the pressure of the entrapped air in tank B. Air is also trapped in line CD as shown. Take p_o = 900 kg/m³ p_W = 1000 kg/m³.

Part 1. If the absolute pressure in a tank is 140 kPa, determine the pressure head in mm of mercury. the atmospheric pressure is 100 kPa.

Part 2. Oxygen in a tank has an absolute pressure of 130 kPa. Determine the pressure head in mm of mercury. The atmospheric pressure is 102 kPa.

a force of 10 N acts on a mass of 5 kg producing an acceleration of 1.5 m/s^2 what is the magnitude of the force of friction acting on the mass

Work, energy, and energy conservation

1. How much work is done on a 2 kg object when it changes its velocity from 20 m/s to 40 m/s?

2. A pile of books of mass 50 kg is placed on top of a cabinet 3 m high. What is the gravitational

potential energy of the pile of books?

3. A box is pulled by a force of 200 N making an angle of 30 degrees with the horizontal. How

much work is done on the box if it is displaced by 20 m?

Four resistance each of R ohms and two resistances each of S ohms are connected (as shown in Fig.

2.50) to four terminasl AB and CD. A p.d. of V votls is applied across the terminals AB and a

resistance

A 1.0 kg block is pushed 3.0 m at a constant velocity up a vertical wall by a constant force applied at an angle of 28.0 ◦ with the horizontal, as shown in the figure. The acceleration of gravity is 9.81 m/s 2.If the coefficient of kinetic friction between the block and the wall is 0.30, find a) the work done by the force on the block.

a. A circular coil has 120 turns of wire in air and has a diameter of 14 cm; the coil is in the same plane as in the sheet. Find the current I that must flow through the wire so that a flux density of 5000µT can be produced at its center

a.   If we immerse a circular coil of 190 mm diameter into a material of relative permeability of 3 and the coil conducts a current of 8A, find the magnetic induction at the center of the coil.

b.   A solenoid with length 65 cm and radius 2 cm has 300 turns of copper wire around a non-magnetic material. If the current flowing through the wire is 3.2A, find the magnetic induction along the center of the solenoid.

a.   Calculate the magnetic induction that exists in air at a distance of 20 mm from a long wire that conducts a current of 6.5A.

b.   Find the magnetic induction B that exists in air at a point located at 15 cm from a long wire that conducts a current of 2A.