Deck 4: The Integral Forms of the Fundamental Laws

Question 1

A 1.2-m high by 2.8-m wide, vertical rectangular gate is used to control the flow of water from a reservoir to a grinding mill. A frictionless hinge runs along the bottom of the gate. The
Minimum force acting normal to and at the very top of the gate needed to hold the gate shut if
The water is at the very top of the gate, is nearest:

A) 6590 N
B) 9800 N
C) 10 000 N
D) 13 300 N How high above the hinge must the water be for the gate
To just open?

Answer 1

6590 N

Question 2

A horizontal 80-cm-diameter hatch is located on the top of a submersible designed for a diver to escape. If the submersible is 100 m below the surface of the ocean, estimate the minimum
Force required to open the hatch? $$\text { Assume } S _ { \text {saltwater } } = 1.02 \text {. }$$

A) 300 kN
B) 400 kN
C) 500 kN
D) 600 kN

Answer 2

500 kN

Question 3

The force P needed to hold the 2-m-radius circular arc gate in the position shown is nearest:

A) 58 kN
B) 49 kN
C) 39 kN
D) 27 kN

Answer 3

49 kN

Question 4

The pressure in the oil (S = 0.86) pipe is 12 kPa. The pressure

A) −34.8 kPa in the water pipe is nearest:

B) −28.8 kPa
C) −18.8 kPa
D) −13.1 kPa

Question 5

An object requires a force of 30 N to hold it under water. The object weighs 90 N in air. Its density is nearest: (A) $850 \mathrm {~kg} / \mathrm { m } ^ { 3 }$
(B) $800 \mathrm {~kg} / \mathrm { m } ^ { 3 }$
(C) $750 \mathrm {~kg} / \mathrm { m } ^ { 3 }$
(D) $700 \mathrm {~kg} / \mathrm { m } ^ { 3 }$

Question 6

A gate automatically opens when the water gets too high.

A) 0.6 m
B) 1.2 m
C) 1.8 m
D) 2.4 m