1
MCQ (Single Correct Answer)

JEE Main 2019 (Online) 11th January Morning Slot

A body of mass 1 kg falls freely from a height of 100 m, on a platform mass 3 kg which is mounted on a spring having spring constant k = 1.25 $$ \times $$ 106 N/m. The body sticks to the platform and the spring's maximum compression is found to be x. Given that g = 10 ms–2 , the value of x will be close to :
A
8 cm
B
4 cm
C
40 cm
D
80 cm

Explanation

velocity of 1 kg block just before it collides with 3kg block

= $$\sqrt {2gh} = \sqrt {2000} $$ m/s

Applying momentum conversation just before and just after collision.

1 $$ \times $$ $$\sqrt {2000} $$ = 4v $$ \Rightarrow $$ v = $${{\sqrt {2000} } \over 4}$$ m/s



initial compression of spring

1.25 $$ \times $$ 106 x0 = 30 $$ \Rightarrow $$ x0 $$ \approx $$ 0

applying work energy theorem,

Wg + Wsp = $$\Delta $$KE

$$ \Rightarrow $$   40 $$ \times $$ x + $${1 \over 2}$$ $$ \times $$ 1.25 $$ \times $$ 106 (02 $$-$$ x2)

= 0 $$-$$ $${1 \over 2}$$ $$ \times $$ 4 $$ \times $$ v2

solving x $$ \approx $$ 4 cm
2
MCQ (Single Correct Answer)

JEE Main 2019 (Online) 12th January Morning Slot

For the given cyclic process CAB as shown for a gas, the work done is :

A
1 J
B
10 J
C
5 J
D
30 J

Explanation

Since P$$-$$V indicator diagram is given, so work done by gas is area under the cyclic diagram.

$$ \therefore $$  $$\Delta $$W = Work done by gas = $${1 \over 2}$$ $$ \times $$ 4 $$ \times $$ 5 J

= 10 J
3
MCQ (Single Correct Answer)

JEE Main 2019 (Online) 12th January Morning Slot

There is a uniform spherically symmetric surface charge density at a distance R0 from the origin. The charge distribution is initially at rest and starts expanding because of mutual repulsion. The figure that represents best the speed V (R(t)) of the distribution as a function of its instantaneous radius R (t) is :
A
B
C
D

Explanation

At any instant 't'

Total energy of charge distribution is constant

i.e.     $${1 \over 2}m{V^2} + {{K{Q^2}} \over {2R}} = 0 + {{K{Q^2}} \over {2{R_0}}}$$

$$ \therefore $$  $${1 \over 2}m{V^2} = {{K{Q^2}} \over {2{R_0}}} - {{K{Q^2}} \over {2R}}$$

$$ \therefore $$  V = $$\sqrt {{2 \over m}{{K{Q^2}} \over 2}.\left( {{1 \over {{R_0}}} - {1 \over R}} \right)} $$

$$ \therefore $$  V = $$\sqrt {{{K{Q^2}} \over m}\left( {{1 \over {{R_0}}} - {1 \over R}} \right)} $$ = C$$\sqrt {{1 \over {{R_0}}} - {1 \over R}} $$

Also the slope of v-s curve will go on decreasing
4
MCQ (Single Correct Answer)

JEE Main 2019 (Online) 12th January Evening Slot

A particle of mass 20 g is released with an initial velocity 5 m/s along the curve from the point A, as shown in the figure. The point A is at height h from point B. The particle slides along the frictionless surface. when the particle reaches point b, its angular momentum about O will be :
(Take g = 10 m/s2)

A
6 kg-m2/s
B
8 kg-m2/s
C
2 kg-m2/s
D
3 kg-m2/s

Explanation

Work Energy Theorem from A to B

Mgh = $${1 \over g}$$ mv$$_B^2$$ $$-$$ $${1 \over g}$$ mv$$_A^2$$

2gh = $$v_B^2 - v_A^2$$

2 $$ \times $$ 10 $$ \times $$ 10 = v$$_B^2$$ $$-$$ 52

vB = 15m/s

Angular momentum about 0

L0 = mvr

= 20 $$ \times $$ 10$$-$$3 $$ \times $$ 20

L0 = 6 kg.m2/s

Questions Asked from Work Power & Energy

On those following papers in MCQ (Single Correct Answer)
Number in Brackets after Paper Name Indicates No of Questions
AIEEE 2002 (2)
keyboard_arrow_right
AIEEE 2003 (4)
keyboard_arrow_right
AIEEE 2004 (5)
keyboard_arrow_right
AIEEE 2005 (5)
keyboard_arrow_right
AIEEE 2006 (4)
keyboard_arrow_right
AIEEE 2007 (1)
keyboard_arrow_right
AIEEE 2008 (2)
keyboard_arrow_right
AIEEE 2010 (1)
keyboard_arrow_right
AIEEE 2012 (1)
keyboard_arrow_right
JEE Main 2014 (Offline) (1)
keyboard_arrow_right
JEE Main 2016 (Offline) (2)
keyboard_arrow_right
JEE Main 2016 (Online) 9th April Morning Slot (1)
keyboard_arrow_right
JEE Main 2016 (Online) 10th April Morning Slot (3)
keyboard_arrow_right
JEE Main 2017 (Offline) (2)
keyboard_arrow_right
JEE Main 2017 (Online) 8th April Morning Slot (1)
keyboard_arrow_right
JEE Main 2017 (Online) 9th April Morning Slot (1)
keyboard_arrow_right
JEE Main 2018 (Offline) (1)
keyboard_arrow_right
JEE Main 2018 (Online) 15th April Evening Slot (1)
keyboard_arrow_right
JEE Main 2018 (Online) 16th April Morning Slot (2)
keyboard_arrow_right
JEE Main 2019 (Online) 9th January Morning Slot (2)
keyboard_arrow_right
JEE Main 2019 (Online) 9th January Evening Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 10th January Morning Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 10th January Evening Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 11th January Morning Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 12th January Morning Slot (2)
keyboard_arrow_right
JEE Main 2019 (Online) 12th January Evening Slot (2)
keyboard_arrow_right
JEE Main 2019 (Online) 8th April Evening Slot (1)
keyboard_arrow_right
JEE Main 2019 (Online) 9th April Morning Slot (2)
keyboard_arrow_right
JEE Main 2019 (Online) 9th April Evening Slot (2)
keyboard_arrow_right
JEE Main 2019 (Online) 12th April Evening Slot (1)
keyboard_arrow_right
JEE Main 2020 (Online) 7th January Morning Slot (2)
keyboard_arrow_right
JEE Main 2020 (Online) 7th January Evening Slot (1)
keyboard_arrow_right
JEE Main 2020 (Online) 9th January Morning Slot (1)
keyboard_arrow_right
JEE Main 2020 (Online) 2nd September Morning Slot (1)
keyboard_arrow_right
JEE Main 2020 (Online) 3rd September Evening Slot (1)
keyboard_arrow_right
JEE Main 2020 (Online) 4th September Morning Slot (1)
keyboard_arrow_right
JEE Main 2020 (Online) 4th September Evening Slot (1)
keyboard_arrow_right
JEE Main 2020 (Online) 6th September Morning Slot (1)
keyboard_arrow_right
JEE Main 2021 (Online) 26th February Morning Shift (1)
keyboard_arrow_right
JEE Main 2021 (Online) 17th March Morning Shift (1)
keyboard_arrow_right
JEE Main 2021 (Online) 18th March Morning Shift (1)
keyboard_arrow_right
JEE Main 2021 (Online) 20th July Evening Shift (1)
keyboard_arrow_right
JEE Main 2021 (Online) 22th July Evening Shift (1)
keyboard_arrow_right
JEE Main 2021 (Online) 27th July Evening Shift (2)
keyboard_arrow_right
JEE Main 2021 (Online) 31st August Evening Shift (1)
keyboard_arrow_right

EXAM MAP

Joint Entrance Examination

JEE Advanced JEE Main

Graduate Aptitude Test in Engineering

GATE CSE GATE ECE GATE ME GATE PI GATE EE GATE CE GATE IN

Medical

NEET