2015 - JAMB Physics Past Questions and Answers - page 4
31
A zinc has a heat capacity of 40 J/K, what is the mass of the zinc, given that the specific heat of zinc is 380 J/kg k
A
0.11kg
B
0.12kg
C
0.13kg
D
0.14kg
correct option: a
Heat capacity (o) = mass (kg) specific heat of a substance (C2)
i.e Q = MC
where Q = 40 J/L, m = ?(380 J/Kgk)
40 = m × 380
m = 0.11kg (Approx)
Users' Answers & Commentsi.e Q = MC
where Q = 40 J/L, m = ?(380 J/Kgk)
40 = m × 380
m = 0.11kg (Approx)
32
If a ball released from a height of 20m, How long would it take the ball to reach the ground? (assures g = 10m/s)
A
2sec
B
3sec
C
35sec
D
2.4sec
correct option: a
Using the equation
S = ut + ½ gt2
H = s = 20m, t = ?
G =10m/s2, u = 0m/s
20 = 0 × t × ½ × 10 t
20 = 5t
i.e 5t2 = 20
t = 20/5 = 4
t = 4 (squaring both sides)
√ t2 = √4
= 2sec
∴ t = 2sec
Users' Answers & CommentsS = ut + ½ gt2
H = s = 20m, t = ?
G =10m/s2, u = 0m/s
20 = 0 × t × ½ × 10 t
20 = 5t
i.e 5t2 = 20
t = 20/5 = 4
t = 4 (squaring both sides)
√ t2 = √4
= 2sec
∴ t = 2sec
33
If the velocity ratio of a machine is 5. What is its ratio of x and y?
A
2 : 5
B
1 : 5
C
5 : 1
D
3 : 1
correct option: c
Velocity Ratio (V.R) = distance moved by the effort (x)÷ distance moved by the load (y)
i.e. V.R = x/y
v. R = 5, x/y = ?
i.e x/y = 5/1; , where x = 5, y = 1
x : y = 5 : 1
Users' Answers & Commentsi.e. V.R = x/y
v. R = 5, x/y = ?
i.e x/y = 5/1; , where x = 5, y = 1
x : y = 5 : 1
34
If the mechanical advantage of a machine is 4. What is its ratio for LOAD to EFFORT?
A
4:01
B
1:04
C
5:01
D
2:01
correct option: a
Mechanical advantage (M.A) of a machine is the ratio of its load to effort
Mathematically
Mechanical advantage (M.A) = Load (L) ÷ Effort (E)
In symbol M.A = L/E
Note:Mechanical (advantages has no S.I unit)
If M.A = 4 then,
L/E = 4/1
The ratio of load to effort = 4 : 1 respectively
Users' Answers & CommentsMathematically
Mechanical advantage (M.A) = Load (L) ÷ Effort (E)
In symbol M.A = L/E
Note:Mechanical (advantages has no S.I unit)
If M.A = 4 then,
L/E = 4/1
The ratio of load to effort = 4 : 1 respectively
35
For a best result using temperature to achieve an accurate measurement, it is best to use
A
Mercury thermometer
B
gas thermometer
C
clinical thermometer
D
alcohol thermometer
correct option: b
A gas thermometers are more besting use to achieve an accurate temperature than others, such as liquid in glass thermometers such as mercury, clinical and alcohol thermometer
Users' Answers & Comments36
A structural engineer stood on a top of a building releasing a light and heavy object to the ground which of the following statement is true?(Neglect Air Resistance)
A
Bothe light and heavy subject reach the ground at the same time
B
he light object get to the ground first before the heavy object
C
he heavy object to the ground first before the light object
D
None get to the ground first
correct option: a
(Neglect of Air resistance)
Note: Both objects reach the ground at the same time
Users' Answers & CommentsNote: Both objects reach the ground at the same time
37
If an object which mass is 3kg moves in a circular path of a radius 0.7m, record a speed at 2m/s what is the result of the angular velocity?
A
4 rads–1
B
1rads–1–1
C
3–1rads–1
D
4rads–1–1
correct option: c
M= 3kg, r = 0.7m, v = 2m/s
v = wr
w = angular velocity
r = radius in an tangential circular
v = speed of an object
W = V/δ = 2/ 0.7 = 2.85
W = 2.853rads–1 (total interest whole number)
W = &approx.; 3rads–1Angular velocity (w) = 3rads–1
Users' Answers & Commentsv = wr
w = angular velocity
r = radius in an tangential circular
v = speed of an object
W = V/δ = 2/ 0.7 = 2.85
W = 2.853rads–1 (total interest whole number)
W = &approx.; 3rads–1Angular velocity (w) = 3rads–1
38
The optical instrument which is suitable for viewing a nearby objects is ………..?
A
Telescope
B
sextant
C
microscope
D
periscope
39
The symbol −10X used to represent which of the particles?
A
Proton
B
Neutron
C
Electrons
D
Atoms
correct option: c
Electron: A sub–atomic particle haring a negative charge and orbiting the nucleus (note: the symbol 0–1e represent the particle of an electrons.)
Users' Answers & Comments40
A radioactive source emits X–rays of very short wavelength (10 -13m ) what is the frequently of these rays?
A
2 × 1018HZ
B
3 × 10 19HZ
C
3 × 1021HZ
D
3 × 10-19HZ
correct option: c
Wavelength (Λ) = 10 -13m
Speed of X-ray = speed of light C = 3×103m/s
Frequently (f) = ?
Using V = fΛ (or (– f π for electromagnetic wave)
f = c/Λ = 3 × 108 ÷ 10-13 = 3 × 103 × 103
= 3 × 1013 × 1013
= 3 × 1021HZ
Users' Answers & CommentsSpeed of X-ray = speed of light C = 3×103m/s
Frequently (f) = ?
Using V = fΛ (or (– f π for electromagnetic wave)
f = c/Λ = 3 × 108 ÷ 10-13 = 3 × 103 × 103
= 3 × 1013 × 1013
= 3 × 1021HZ