PPSC PHYSICS-Measurements, Units & Vectors
01-The SI standard of time is based on:
The daily rotation of the earth
The frequency of light emitted by Kr-86
The yearly revolution of the earth about the sun
A precision pendulum clock
None of these
02-A nanosecond is:
10^9 s
10^-9 s
10^-10 s
10^-7
10^-12
03-The SI standard of length is based on:
The distance from the north pole to the equator along a meridian passing through Paris
Wavelength of light emitted by Hg-198
Wavelength of light emitted by Kr-86
A precision meter stick in Paris
The speed of light
04-In 1806, the U.S. Congress defined the U.S yard as exactly 3600/3937 international meter. This was done primarily because
Length can be measured more accurately in meters than
The meter is more stable than the yard
This definition relates the common U.S length units to a more widely used system
There are more wavelengths in a yard than in a meter
The memebers of this Congress
05-Which of the following is closest to a yard in length?
0.01 m
0.1 m
1 m
100 m
1000 m
06-There is no SI base unit for area because:
an area has no thickness; hence no physical standard can be built
we live in a three (not a two) dimensional world
It is impossible to express square feet in terms of meters
area can be expressed in terms of square meters
Area is not an important physical quantity
07-The SI base unit for mass is:
Gram
Pound
Kilogram
Ounce
Kilopound
08-A gram is:
10−6 kg
10−3 kg
1 kg
103 kg
106 kg
09-Which of the following weighs about a pound?
0.05 kg
0.5 kg
5 kg
450 g
500 kg
10- (5.0 × 104) × (3.0 × 106) =
1.5 × 10^9
1.5 × 10^10
1.5 × 10^11
1.5 × 10^12
1.5 × 10^13
11-The number of significant figures in 0.00150 is:
2
3
4
5
6
12-The number of significant figures in 15.0 is:
1
2
3
5
4
13- 1 mi is equivalent to 1609 m so 55 mph is:
15 m/s
25 m/s
66 m/s
88 m/s
1500 m/s
14- A right circular cylinder with a radius of 2.3 cm and a height of 1.4 m has a volume of:
0.20 m3
0.14 m3
9.3 × 10^−3 m3
2.3 × 10^−3 m3
7.4 × 10−4 m3
15-During a short interval of time the speed v in m/s of an automobile is given by v = at2 + bt3, where the time t is in seconds. The units of a and b are respectively:
M · s2; m · s4
s3/m; s4/m
m/s 2 ; m/s 3
m/s 3 ; m/s 4
M/s 4 ; m/s 5
16-We say that the displacement of a particle is a vector quantity. Our best justification for this assertion is:
displacement can be specified by a magnitude and a direction
operating with displacements according to the rules for manipulating vectors leads to results in agreement with experiments
a displacement is obviously not a scalar
Displacement can be specified by three numbers
displacement is associated with motion
17- A vector of magnitude 3 CANNOT be added to a vector of magnitude 4 so that the magnitude of the resultant is:
Zero
1
3
5
7
18-A vector of magnitude 20 is added to a vector of magnitude 25. The magnitude of this sum might be:
Zero
3
12
47
50
19- A vector S of magnitude 6 and another vector T have a sum of magnitude 12. The vector T:
must have a magnitude of at least 6 but no more than 18
may have a magnitude of 20
cannot have a magnitude greater than 12
Must be perpendicular to Sn
must be perpendicular to the vector sum
20- The vector −A is:
greater than A in magnitude
less than A in magnitude
in the same direction as A
in the direction opposite to A
perpendicular to A
21- A vector has a magnitude of 12. When its tail is at the origin it lies between the positive x axis and the negative y axis and makes an angle of 30◦ with the x axis. Its y component is:
6/ √3
�6 √3
6
-6
12
22-If the x component of a vector A, in the xy plane, is half as large as the magnitude of the vector, the tangent of the angle between the vector and the x axis is:
√ 3
1/2
√ 3/2
3/2
3
23- If vector A = (6 m)ˆi − (8 m)ˆj then vector 4A has magnitude:
10 m
20 m
30 m
40 m
50 m
24-A vector has a component of 10 m in the +x direction, a component of 10 m in the +y direction, and a component of 5 m in the +z direction. The magnitude of this vector is:
0
15 m
20 m
25 m
225 m
25-A vector in the xy plane has a magnitude of 25 m and an x component of 12 m. The angle it makes with the positive x axis is:
26'
29'
61'
64'
241'
26- The angle between vector A = (25 m)ˆi + (45 m)ˆj and the positive x axis is:
29'
61'
151'
209'
241'
27- A certain vector in the xy plane has an x component of 4 m and a y component of 10 m. It is then rotated in the xy plane so its x component is doubled. Its new y component is about:
20 m
7.2 m
5.0 m
4.5 m
2.2 m
28-Vectors A and B each have magnitude L. When drawn with their tails at the same point, the angle between them is 30◦. The value of vectors A · B is:
Zero
L^2
√ 3L^2/2
2L^2
NONE OF THESE
29-Two vectors have magnitudes of 10 m and 15 m. The angle between them when they are drawn with their tails at the same point is 65◦. The component of the longer vector along the line of the shorter is:
ZERO
4.2 m
6.3 m
9.1 m
14 m
30-If the magnitude of the sum of two vectors is less than the magnitude of either vector, then:
The scalar product of the vectors must be negative
the scalar product of the vectors must be positive
The vectors must be parallel and in opposite directions
the vectors must be parallel and in the same direction
none of the above
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