NEON PHYSICS
JEE ADVANCED REVSION SHEET-4 [FRICTION]
1. A block of mass m is placed on a horizontal surface. The coefficient of friction between them is . The block has
to be moved by applying a single external force on it. The force may be applied in any direction. What is this
minimum force?
(a) mg applied vertically upwards if > 1 (b) mg applied horizontally if < 1
mg 2 mg
(c*) for all values of (d) for all values of
2 + 1 2 + 1
3L
2. A uniform chain length L has one of its end attached to the wall at point A, while of the length of the chain is
4
lying on table as shown in figure. The minimum coefficient of friction between table and chain so that remains in
equilibrium is:
A
37
(a) 1/3 (b) 1/4 (c) 3/4 (d) 1/5
Ans. (B)
L F
Fcos37o = g
4
F sin 37o = T = f
3Lg
f= N T T f
16 L
g
1 1 4
min =
4 4
3. Two block of masses 2 kg and 4 kg are connected through a massless inextensible string. The co–efficient of
friction between 2 kg block and ground is 0.4 and the coefficient of friction between 4 kg block and ground is 0.6
Two forces F1 = 10 N and F2 = 20 N are applied on the blocks as shown in the figure. Calculates the frictional
force between 4 kg block and ground (Assume initially the tension in the string was just zero before forces F 1
and F2 were applied)
F1 = 10 N 2kg 4kg F2 = 20 N
1 = 0.4 2 = 0.6
(a) 24 N (b) 8N (c) 18 N (d) 10 N
Ans. (C) 10N 2kg T
System will not move (Equilibrium)
For equilibrium of 2 kg block f 1 = 8N
10 = 8 + T
T = 2N T 4kg 20 N
For equilibrium of 4 kg block f2
T + f2 = 20
f2 = 18 N
4. In the arrangement shown in figure, coefficient of friction between the two blocks is = 1/ 2 . The force of friction
acting between the two blocks is
(a*) 8N (b) 10 N (c) 6N (d) 4N
5. Fig. shows three blocks in contact sliding down an inclined plane. If µ1, µ2 and µ3 are coefficient of friction
between the plane and blocks m1, m2 and m3 respectively. Then
SHIKHAR : Indra Complex Vijaya Nagar, Chetakpuri Gwalior 0751-3551081 1
, NEON PHYSICS
3
m
m2
1
m
(a) If µ1 > µ2 > µ3, then all the blocks will move together.
(b) If µ1 < µ2 < µ3, then all the blocks move together
(c) If µ1 < µ2 > µ3, then m1 and m2 will move together an m3 gets separated.
(d) If µ1 < µ2 > µ3, then m2 and m3 must move together and m1 essentially get separated.
Ans. (A)
a = g [sin – cos ]
6. Horizontal surface is rough for the blocks. If ‘f’ is the magnitude of frictional force developed between the block
‘B’ and plane. Then choose the correct graph.
B A
m m F
f f f f
F F F F
(A) (B*) (C) (D)
7. A block of mass m is placed on a surface with a vertical cross section given by y = x3/6. If the coefficient of
friction is 0.5, the maximum height above the ground at which the block can be placed without slipping is
1 1 1 2
(a) m (b) m (*c) m (d) m
3 2 6 3
8. Given in the figure are two blocks A and B of weight 20 N and 100 N, respectively. These
are being pressed against a wall by a force F as shown. IF the coefficient of friction between
the blocks is 0.1 and between block B and the wall is 0.15, the frictional force applied by
the wall on block B is
(a) 100 N (b) 80 N (c*) 120 N (d) 150 N
9. A block A of mass m is placed cover a plank B of mass 2m. Plank B is placed over a smooth horizontal surface.
The coefficient of friction between A and B is 0.5. Block A is given a velocity 0 towards right. Acceleration of B
relative to A is
(a) g/2 (b) g (c*) 3g/4 (d) Zero
10. A man of mass 50 kg is pulling on a plank of mass 100 kg kept on smooth floor as shown with force of 100N. If
both man & plank move together, find force of friction acting on man
100 100
(a*) N towards left (b) N towards right
3 3
250 250
(c) N towards left (d) N towards right
3 3
11. In the arrangement shown in figure, coefficient of friction between the two blocks is = 1/ 2. The force of friction
acting between the two blocks is
SHIKHAR : Indra Complex Vijaya Nagar, Chetakpuri Gwalior 0751-3551081 2
JEE ADVANCED REVSION SHEET-4 [FRICTION]
1. A block of mass m is placed on a horizontal surface. The coefficient of friction between them is . The block has
to be moved by applying a single external force on it. The force may be applied in any direction. What is this
minimum force?
(a) mg applied vertically upwards if > 1 (b) mg applied horizontally if < 1
mg 2 mg
(c*) for all values of (d) for all values of
2 + 1 2 + 1
3L
2. A uniform chain length L has one of its end attached to the wall at point A, while of the length of the chain is
4
lying on table as shown in figure. The minimum coefficient of friction between table and chain so that remains in
equilibrium is:
A
37
(a) 1/3 (b) 1/4 (c) 3/4 (d) 1/5
Ans. (B)
L F
Fcos37o = g
4
F sin 37o = T = f
3Lg
f= N T T f
16 L
g
1 1 4
min =
4 4
3. Two block of masses 2 kg and 4 kg are connected through a massless inextensible string. The co–efficient of
friction between 2 kg block and ground is 0.4 and the coefficient of friction between 4 kg block and ground is 0.6
Two forces F1 = 10 N and F2 = 20 N are applied on the blocks as shown in the figure. Calculates the frictional
force between 4 kg block and ground (Assume initially the tension in the string was just zero before forces F 1
and F2 were applied)
F1 = 10 N 2kg 4kg F2 = 20 N
1 = 0.4 2 = 0.6
(a) 24 N (b) 8N (c) 18 N (d) 10 N
Ans. (C) 10N 2kg T
System will not move (Equilibrium)
For equilibrium of 2 kg block f 1 = 8N
10 = 8 + T
T = 2N T 4kg 20 N
For equilibrium of 4 kg block f2
T + f2 = 20
f2 = 18 N
4. In the arrangement shown in figure, coefficient of friction between the two blocks is = 1/ 2 . The force of friction
acting between the two blocks is
(a*) 8N (b) 10 N (c) 6N (d) 4N
5. Fig. shows three blocks in contact sliding down an inclined plane. If µ1, µ2 and µ3 are coefficient of friction
between the plane and blocks m1, m2 and m3 respectively. Then
SHIKHAR : Indra Complex Vijaya Nagar, Chetakpuri Gwalior 0751-3551081 1
, NEON PHYSICS
3
m
m2
1
m
(a) If µ1 > µ2 > µ3, then all the blocks will move together.
(b) If µ1 < µ2 < µ3, then all the blocks move together
(c) If µ1 < µ2 > µ3, then m1 and m2 will move together an m3 gets separated.
(d) If µ1 < µ2 > µ3, then m2 and m3 must move together and m1 essentially get separated.
Ans. (A)
a = g [sin – cos ]
6. Horizontal surface is rough for the blocks. If ‘f’ is the magnitude of frictional force developed between the block
‘B’ and plane. Then choose the correct graph.
B A
m m F
f f f f
F F F F
(A) (B*) (C) (D)
7. A block of mass m is placed on a surface with a vertical cross section given by y = x3/6. If the coefficient of
friction is 0.5, the maximum height above the ground at which the block can be placed without slipping is
1 1 1 2
(a) m (b) m (*c) m (d) m
3 2 6 3
8. Given in the figure are two blocks A and B of weight 20 N and 100 N, respectively. These
are being pressed against a wall by a force F as shown. IF the coefficient of friction between
the blocks is 0.1 and between block B and the wall is 0.15, the frictional force applied by
the wall on block B is
(a) 100 N (b) 80 N (c*) 120 N (d) 150 N
9. A block A of mass m is placed cover a plank B of mass 2m. Plank B is placed over a smooth horizontal surface.
The coefficient of friction between A and B is 0.5. Block A is given a velocity 0 towards right. Acceleration of B
relative to A is
(a) g/2 (b) g (c*) 3g/4 (d) Zero
10. A man of mass 50 kg is pulling on a plank of mass 100 kg kept on smooth floor as shown with force of 100N. If
both man & plank move together, find force of friction acting on man
100 100
(a*) N towards left (b) N towards right
3 3
250 250
(c) N towards left (d) N towards right
3 3
11. In the arrangement shown in figure, coefficient of friction between the two blocks is = 1/ 2. The force of friction
acting between the two blocks is
SHIKHAR : Indra Complex Vijaya Nagar, Chetakpuri Gwalior 0751-3551081 2
