Unit 1 Engineering Physics

1.14 Exercises.....................................

1.14 Exercises

Objective Type [ 8 ]

1.1A rope 1 cm in diameter breaks if the
tension in it exceeds 500 N. The maximum
tension that may be given to similar rope of
diameter 2 cm is
(A) 500 N (B) 250 N
(C) 1000 N (D) 2000 N.

1.2The most important factor upon which
breaking stress of a wire depends on is
(A) material of the wire
(B) length of the wire
(C) radius of the wire
(D) shape of cross-section.

1.3A wire can sustain the weight of 20 kg
before breaking If the wire is cut into two
equal parts, each part can sustain a weight
of
(A) 10 kg (B) 20 kg (C) 40 kg (D) 80 kg.

1.4Two wires A and B are made of same
material. The wire A has a lengthland
diameterrwhile the wire B has a length
2 land diameterr/ 2. If the two wires are
stretched by the same force, the elongation
in A divided by the elongation in B is
(A) 1/8 (B) 1/4 (C) 4 (D) 8

1.5A wire elongates by 1.0 mm when a
load W is hung from it. If the wire goes
over a pulley and two weights W each are
hung at the two ends, the elongation of the
wire will be
(A) 0.5 m (B) 1.0 mm

(C) 2.0 mm (D) 4.0 mm.

1.6A heavy uniform rod is hanging verti-

cally from a fixed support. It is stretched

by its own weight. The diameter the red is

(A) smallest at the top and gradually in-

creases down the rod

(B) largest at the top and gradually de-

creases down the rod

(C) uniform everywhere

(D) maximum at the middle

1.7When a metal wire is stretched by a

load, the fractional change in its volume

V/Vs proportional to

(A)l/l (B)(l/l)^2 (C)

Ò

l/l

(D) none of these.

1.8The length of a metal wire isl 1 when

the tension in it isT 1 andl 2 when the ten-

sion is T 2. When there is no tension, its

length is

(A)l^1 + 2 l^2 (B)

Ò

l 1 /l 2

(C)l^1 TT^22 ≠≠Tl^21 T^1 (D)l^1 TT^22 ++Tl^21 T^1

1.9A heavy mass is attached to thin wire

and la whirled in vertical circle. The wire is

more likely to break

(A) when the mass la at the highest point

(B) when the mass is at the lowest point

(C) when the wire is horizontal

(C) when the wire makes 45ofrom the up-

ward vertical

Problems

1.10 Free end of a given cantilever de-
presses 5 mm under a certain load. Cal-
culate the depression produced under the
same load for another cantilever of the same

material and cross-section but with length

thrice as that of the original one [ 6 ].

PH8151 41 LICET