1
WB JEE 2020
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Consider the vectors $$A = \hat i + \hat j - \hat k$$ ,$$B = 2\hat i - \hat j + \hat k$$ and $$C = {1 \over {\sqrt 5 }}\left( {\hat i - 2\hat j + 2\hat k} \right)$$ . What is the value of C. (A$$ \times $$ B) ?
A
1
B
0
C
3$${\sqrt 2 }$$
D
18$${\sqrt 5 }$$
2
WB JEE 2020
MCQ (Single Correct Answer)
+1
-0.25
Change Language
A fighter plane, flying horizontally with a speed 360 km/h at an altitude of 500 m drops a bomb for a target straight ahead of it on the ground. The bomb should be dropped at what approximate distance ahead of the target? Assume that acceleration due to gravity (g) is 10 ms-2. Also, neglect air drag.
A
1000 m
B
50$${\sqrt 5 }$$ m
C
500$${\sqrt 5 }$$ m
D
866 m
3
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
4
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
$$\theta {{2\varepsilon } \over {\varepsilon + 1}}$$
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