# Physics (2018) | Study Mode

Question 71
A
60N and 60$$^o$$
B
60N and 30$$^o$$
C
20?3 N and 60$$^o$$
D
20?3N and 30$$^o$$
##### Explanation

Resolve vertically, 40cos = 20, = 60$$^o$$

Resolve horizontally, f = 40sin = 40sin60$$^o$$

= 40($$\frac{\sqrt{3}}{2}$$)

= 203 N

Question 72
A
Conduction
B
Convection
C
Expansion
D
##### Explanation

Conduction: the flow of internal energy from a region of higher temperature to lower temperature
Convection: heat transfer due to bulk movement of molecules within fluids
Expansion: the action of becoming larger or more extensive

Question 73
A
Capillary
B
Surface
C
Viscosity
D
Cohesion
##### Explanation

Viscosity, resistance of a fluid (liquid or gas) to a change in shape, or movement of neighboring portions relative to one another. Viscosity denotes opposition to flow. The reciprocal of the viscosity is called the fluidity, a measure of the ease of flow. Molasses, for example, has a greater viscosity than water. Because part of a fluid that is forced to move carries along to some extent adjacent parts, viscosity may be thought of as internal friction between the molecules; such friction opposes the development of velocity differences within a fluid. Viscosity is a major factor in determining the forces that must be overcome when fluids are used in lubrication and transported in pipelines. It controls the liquid flow in such processes as spraying, injection molding, and surface coating.

Question 74
A
$$\frac{M1V1}{M-M1}$$
B
$$\frac{M1V1}{M1-M}$$
C
$$\frac{M1V1}{M}$$
D
$$\frac{MV}{M-M1}$$
##### Explanation

Question 75
A
$$\frac{P}{v}$$
B
($$\frac{1}{2}$$)V
C
PV
D
$$\frac{P}{V^2}$$
##### Explanation

P = F $$\frac{S}{1}$$
P = F x V
F = $$\frac{P}{V}$$

Question 76
A

ML$$^{-1}$$T$$^{-2}$$

B

MLT$$^{-2}$$

C

ML$$^{2}$$T$$^{3}$$

D

ML$$^{-3}$$

##### Explanation

Pressure = $$\frac{Force}{Area}$$

Pressure = m $$\frac{a}{t}$$

= $$\frac{MLT^{2}}{L L}$$

= ML$$^{1}$$T$$^{2}$$

Question 77
A
Molecules are given energy during the heating
B
Friction between oil layers is reduced
C
Oil molecules force each other out
D
Adhesion between the oil molecules and those of the bottle is increased
##### Explanation

Molecules cannot be given energy during the heating and the molecules of oil cannot force each other out

Question 78
A
20.0kgms$$^{-1}$$
B
10.0kgms$$^{-1}$$
C
5.0kgms$$^{-1}$$
D
2.5kgms$$^{-1}$$
##### Explanation

Impulse = Change in momentum

m (v - u)

5 (2.0)

= 5 x 2 = 10.0kgm$$^{-1}$$

= 10.0kgms$$^{-1}$$

Question 79
A
$$\frac{E1}{E2}$$
B
$$\frac{E3}{E2}$$
C
$$\frac{E2}{E1}$$+ E2
D
$$\frac{E2}{E3}$$ + E1
##### Explanation

Efficiency = $$\frac{\text{useful energy output from machine}}{\text{energy input into machine}}$$

= $$\frac{E3}{E2}$$

Question 80
A
25.2N
B
17.4N
C
12.6N
D
9.0N
##### Explanation

Weight of water displaced = upthrust = 30 - 21 = 9N

Mass of water displaced = $$\frac{9}{10}$$ = 0.9kg

Volume of object = 9 10$$^{-4}$$m$$^3$$

= (9 10$$^{-4}$$) (1.4 103)

= 1.26kg = 12N

30 - 12.6 = 17.4N

Try this quiz in in E-test/CBT Mode
switch to