1
NEET 2018
MCQ (Single Correct Answer)
+4
-1
Two wires are made of the same material and have the same volume. The first wire has cross-sectional area A and the second wire has cross-sectional area 3A. If the length of the first wire is increased by $$\Delta $$l on applying a force F, how much force is needed to stretch the second wire by the same amount?
A
6F
B
F
C
9F
D
4F
2
NEET 2018
MCQ (Single Correct Answer)
+4
-1
The power radiated by a black body is P and it radiates maximum energy at wavelength, $$\lambda $$0 . If the temperature of the black body is now changed so that it radiates maximum energy at wavelength $${3 \over 4}{\lambda _0}$$, the power radiated by it becomes nP. The value of n is
A
$${3 \over 4}$$
B
$${4 \over 3}$$
C
$${{256} \over {81}}$$
D
$${{81} \over {256}}$$
3
NEET 2018
MCQ (Single Correct Answer)
+4
-1
Three objects, A : (a solid sphere), B : (a thin circular disk) and C : (a circular ring), each have the same mass M and radius R. They all spin with the same angular speed $$\omega $$ about their own symmetry axes. The amounts of work (W) required to bring them to rest, would satisfy the relation
A
WC > WB > WA
B
WA > WB > WC
C
WB > WA > WC
D
WA > WC > WB
4
NEET 2018
MCQ (Single Correct Answer)
+4
-1
The moment of the force, $$\overrightarrow F = 4\widehat i + 5\widehat j - 6\widehat k$$ at
(2, 0, –3), about the point (2, –2, –2), is given by
A
$$ - 8\widehat i - 4\widehat j - 7\widehat k$$
B
$$ - 4\widehat i - \widehat j - 8\widehat k$$
C
$$ - 7\widehat i - 8\widehat j - 4\widehat k$$
D
$$ - 7\widehat i - 4\widehat j - 8\widehat k$$
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