1
NEET 2018
MCQ (Single Correct Answer)
+4
-1
Change Language
At what temperature will the rms speed of oxygen molecules become just sufficient for escaping from the Earth’s atmosphere?
(Given : Mass of oxygen molecule (m) = 2.76 × 10–26 kg, Boltzmann’s constant kB = 1.38 × 10–23 J K–1)
A
2.508 × 104 K
B
8.360 × 104 K
C
5.016 × 104 K
D
1.254 × 104 K
2
NEET 2018
MCQ (Single Correct Answer)
+4
-1
Change Language
An object is placed at a distance of 40 cm from a concave mirror of focal length 15 cm. If the object is displaced through a distance of 20 cm towards the mirror, the displacement of the image will be
A
30 cm away from the mirror
B
36 cm away from the mirror
C
30 cm towards the mirror
D
36 cm towards the mirror
3
NEET 2018
MCQ (Single Correct Answer)
+4
-1
Change Language
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
Change Language
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