1
WB JEE 2020
MCQ (Single Correct Answer)
+1
-0.25
Change Language
A block of mass m rests on a horizontal table with a coefficient of static friction $$\mu $$. What minimum force must be applied on the block to drag it on the table?
A
$${\mu \over {\sqrt {1 + {\mu ^2}} }}$$ mg
B
$${{\mu - 1} \over {\mu + 1}}$$ mg
C
$${\mu \over {\sqrt {1 - {\mu ^2}} }}$$ mg
D
$$\mu $$ mg
2
WB JEE 2020
MCQ (Single Correct Answer)
+1
-0.25
Change Language
A tennis ball hits the floor with a speed v at an angle $$\theta $$ with the normal to the floor. If the collision is inelastic and the coefficient of restitution is $$\varepsilon $$, what will be the angle of reflection?
A
$${\tan ^{ - 1}}\left( {{{\tan \theta } \over \varepsilon }} \right)$$
B
$${\sin ^{ - 1}}\left( {{{\sin \theta } \over \varepsilon }} \right)$$
C
$$\theta $$$$\varepsilon $$
D
$$\theta {{2\varepsilon } \over {\varepsilon + 1}}$$
3
WB JEE 2020
MCQ (Single Correct Answer)
+1
-0.25
Change Language
The bob of a swinging second pendulum (one whose time period is 2 s) has a small speed v0 at its lowest point. It height from this lowest point 2.25 s after passing through it, is given by
A
$${{v_0^2} \over {2g}}$$
B
$${{v_0^2} \over {g}}$$
C
$${{v_0^2} \over {4g}}$$
D
$${{9v_0^2} \over {4g}}$$
4
WB JEE 2020
MCQ (Single Correct Answer)
+1
-0.25
Change Language
A steel and a brass wire, each of length 50 cm and cross-sectional area 0.005 cm2 hang from a ceiling and are 15 cm apart. Lower ends of the wires are attached to a light horizontal bar. A suitable downward load is applied to the bar, so that each of the wires extends in length by 0.1 cm. At what distance from the steel wire, the load must be applied?

[Young's modulus of steel = 2 $$ \times $$ 1012 dyne/cm2 and that of brass = 1 $$ \times $$ 1012 dyne/cm2]
A
7.5 cm
B
5 cm
C
10 cm
D
3 cm
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