JEE Main Previous Year Questions (2021-2026): Laws of Motion

 Page 1


JEE Main Previous Year Questions (2021-2026): 
Laws of Motion  
 
(January 2026) 
 
Q1: A small block of mass m slides down from the top of a frictionless inclined surface, 
while the inclined plane is moving towards left with constant acceleration a
0
. The angle 
between the inclined plane and ground is ? and its base length is L. Assuming that 
initially the small block is at the top of the inclined plane, the time it takes to reach the 
lowest point of the inclined plane is ________. 
 
(a)  
(b)  
Page 2


JEE Main Previous Year Questions (2021-2026): 
Laws of Motion  
 
(January 2026) 
 
Q1: A small block of mass m slides down from the top of a frictionless inclined surface, 
while the inclined plane is moving towards left with constant acceleration a
0
. The angle 
between the inclined plane and ground is ? and its base length is L. Assuming that 
initially the small block is at the top of the inclined plane, the time it takes to reach the 
lowest point of the inclined plane is ________. 
 
(a)  
(b)  
(c)  
(d)  
Ans: (b) 
Sol:  
The length of the incline (hypotenuse) is given by: 
 
 
Since the wedge is accelerating to the left with a
0
, we must work in the non-inertial frame of the 
wedge. This causes a pseudo-force (ma
0
) acting on the block to the right. 
We resolve all forces along the surface of the incline : 
Page 3


JEE Main Previous Year Questions (2021-2026): 
Laws of Motion  
 
(January 2026) 
 
Q1: A small block of mass m slides down from the top of a frictionless inclined surface, 
while the inclined plane is moving towards left with constant acceleration a
0
. The angle 
between the inclined plane and ground is ? and its base length is L. Assuming that 
initially the small block is at the top of the inclined plane, the time it takes to reach the 
lowest point of the inclined plane is ________. 
 
(a)  
(b)  
(c)  
(d)  
Ans: (b) 
Sol:  
The length of the incline (hypotenuse) is given by: 
 
 
Since the wedge is accelerating to the left with a
0
, we must work in the non-inertial frame of the 
wedge. This causes a pseudo-force (ma
0
) acting on the block to the right. 
We resolve all forces along the surface of the incline : 
 
The net acceleration relative to the incline (a
rel
) is: 
 
Using the kinematic equation for distance s starting from rest (u = 0): 
Page 4


JEE Main Previous Year Questions (2021-2026): 
Laws of Motion  
 
(January 2026) 
 
Q1: A small block of mass m slides down from the top of a frictionless inclined surface, 
while the inclined plane is moving towards left with constant acceleration a
0
. The angle 
between the inclined plane and ground is ? and its base length is L. Assuming that 
initially the small block is at the top of the inclined plane, the time it takes to reach the 
lowest point of the inclined plane is ________. 
 
(a)  
(b)  
(c)  
(d)  
Ans: (b) 
Sol:  
The length of the incline (hypotenuse) is given by: 
 
 
Since the wedge is accelerating to the left with a
0
, we must work in the non-inertial frame of the 
wedge. This causes a pseudo-force (ma
0
) acting on the block to the right. 
We resolve all forces along the surface of the incline : 
 
The net acceleration relative to the incline (a
rel
) is: 
 
Using the kinematic equation for distance s starting from rest (u = 0): 
 
 
Hence, the correct option is (b). 
 
Q2: A block of mass 5 kg is moving on an inclined plane which makes an angle of 30
°
 
with the horizontal. Friction coefficient between the block and inclined plane surface is 
v3/2. The force to be applied on the block so that the block will move down without 
acceleration is ____N. 
(g = 10 m/s
2
) 
(a) 25 
(b) 12.5 
(c) 15 
(d) 7.5 
Ans: (b) 
Sol:  
The forces acting on the block are, 
Page 5


JEE Main Previous Year Questions (2021-2026): 
Laws of Motion  
 
(January 2026) 
 
Q1: A small block of mass m slides down from the top of a frictionless inclined surface, 
while the inclined plane is moving towards left with constant acceleration a
0
. The angle 
between the inclined plane and ground is ? and its base length is L. Assuming that 
initially the small block is at the top of the inclined plane, the time it takes to reach the 
lowest point of the inclined plane is ________. 
 
(a)  
(b)  
(c)  
(d)  
Ans: (b) 
Sol:  
The length of the incline (hypotenuse) is given by: 
 
 
Since the wedge is accelerating to the left with a
0
, we must work in the non-inertial frame of the 
wedge. This causes a pseudo-force (ma
0
) acting on the block to the right. 
We resolve all forces along the surface of the incline : 
 
The net acceleration relative to the incline (a
rel
) is: 
 
Using the kinematic equation for distance s starting from rest (u = 0): 
 
 
Hence, the correct option is (b). 
 
Q2: A block of mass 5 kg is moving on an inclined plane which makes an angle of 30
°
 
with the horizontal. Friction coefficient between the block and inclined plane surface is 
v3/2. The force to be applied on the block so that the block will move down without 
acceleration is ____N. 
(g = 10 m/s
2
) 
(a) 25 
(b) 12.5 
(c) 15 
(d) 7.5 
Ans: (b) 
Sol:  
The forces acting on the block are, 
 
Component of weight down the plane (along x -axis) 
 
Normal Force, N = mg cos   ?  
Since the block moves down, friction acts up the plane. 
 
Maximum frictional force : 
 
Since the upward frictional force (37.5 N) is greater than the downward component of weight (25 
N), the block will not move down on its own. To make it move down at a constant velocity, an 
additional downward force (P) must be applied.