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8/10/2019 i Physics Lom

1/4

Assignment

FIITJEE

FIITJEE

TOPIC LAWS OF MOTION

1. A rod is placed such that end A is on smooth horizontal floor and end

B on smooth wall, as shown. At an instant velocity of end A is 4 2

m/s. The velocity of end B as seen by an ant at C, moving with a

speed of1

m/s3

is __________ m/s.

(A) 14 23

- (B)1

4 23

(C) 3 3 (D) None of these45

AO

75

B

C

2. An inclined plane makes an angle 300with the horizontal. A groove (OA) of

length = 5m cut in the plane makes an angle 300with OX. A short smooth

cylinder is free to slide down the influence of gravity. The time taken by thecylinder to reach from A to 0 is ( g=10m/s

2)

(A) 4 s (B) 2 s (C) 2.5 s (D) 1 s

3. Two blocks of mass 2m and m are arranged as shown in the figure. The pulley is massless and a forceF isapplied horizontally. If a1is the upward acceleration of m & a is acceleration of

2m horizontally, then 1a

ais (Assume all surfaces to be frictionless)

(A) F

mg (B)

3(F mg)

F

- (C) 3mg

F (D)

F

(F mg)-

4. A body of mass m is placed on an elevator. When the elevator accelerates up and down with equalamount of acceleration, the body experiences normal reactions N1 and N2 respectively. Then theacceleration of the elevator is

(A)1 2

N N

a 2m

-

= (B)1 2

N N

a m

-

= (C)1 2

N N

a m

+

= (D)1 2

N N

a 2m

+

=

5. A force time (Ft) graph for linear motion is shown in thefollowing figure. The segments shown are circular. Thelinear momentum gained between 4 and 8 second is (where F is inNewton, t is in second)

(A) 4pN-s (B) zero(C) 4pN-s (D)+2pN-s

Second

F

1 2 3 45 6 7 8

2

1

1

2

6. A chain of mass m and length L is hanging vertically from a ceiling. The tension at a point L/4 from the

ceiling is(A) mg (B) mg/4 (C) 3mg/4 (D) mg

7. Three equal weights A, B, C of mass 2 kg each are hanging on a string passing over a

fixed frictionless pulley as shown in figure. The tension in the string connecting weights

B and C is

(A) Zero (B) 13 N (C) 3.3 N (D) 19.6 NA B

C


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Assignment

FIITJEE

FIITJEE

8. Three masses of 1 kg, 6 kg and 3 kg are connected to each other

with threads and are placed on a table as shown in figure. What is the

acceleration with which the system is moving? (take g = 10 ms2

)

(A) zero (B) 1 ms2

(C) 2 ms2

(D) 3 ms2

T2

1 kg 3 kg

T2T1

6 kgT1

9. An iron sphere weights 10 N and rusts in a V shaped trough whose sides

form a angle 60. What are the normal forces exerted by the walls on thesphere in case as shown in figure.

(A) RA= 10 N, RB= 0 (B) RA= RB= 10 N

(C) RA= 103, RB=3

10 (D) RA= RB= 5 N

A B

60

10. Two masses M1and M2are attached to the ends of a string which passes

over a pulley attached to the top of a double inclined plane of angles of

inclination aand b. If M2> M1, the acceleration a of the system is givenby

M1 M2

a b

(A) 2

1 2

M (sin )g

M M

b

+ (B) 2

1 2

M (sin )g

M M

a

+ (C) 2 1

1 2

M sin M sin

M M

b - a

+ g (D) zero

11. A wedge of mass M is loaded with a sphere of mass m. If a horizontal force F isapplied on the wedge, it remains in equilibrium. Then

(A) N1= mg sec q, N1= reaction force between wedge and sphere(B) F = mg tan q(C) N2= mg tan q, N2= reaction force between sphere and vertical wall(D) N3= Mg + mg; N3= reaction force between ground and wedge

F

M

mq

12. The figure shows a smooth fixed wedge on which a block of mass m is kept and released then which of

the following are true. Give your answers in given coordinate system

(A) N cos q= mg(B) N = mg cosq

(C)Nsin Ncos mg a i j

m m

q q - = +

r

(D)2 a gsin cos i gsin j= q q - q

r

smooth

fixed

h

y

xq

N

(0, 0)

where ar

= acceleration of block and N is the contact force between the block and the wedge.

Paragraph for Question Nos. 13 to 15

The mass of the block shown is 20 kg

F1= 10 N; F2= 10 2 N & F=5t N ( t in seconds)

If the three coplanar forces start acting on it simultaneously as shown in

the figure, then

F = 5t

45

F2

F1

90

13. The horizontal displacement covered during an interval of 5 seconds from t=0 to t=5s is

(A) 1.9( 2 1) m (B) 19( 2 1) m (C) 380 m (D) zero


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Assignment

FIITJEE

FIITJEE

14. If F1and F2are withdrawn immediately after it leaves the ground and F continues to act, then the

(A) the block falls down (B) the block starts moving again when t = 40 s

(C) again normal reaction becomes zero at 40s (D) all the above statements are correct

15. The direction of 1 2F Fr r

is

(A) opposite to F (B) perpendicular and into the plane of paper(C) perpendicular and out of the plane of paper (D) none of these

16. All the strings and the pullies in the figure shownare massless and frictionless. Find the relationbetween the accelerations of the block B and massm as shown in the figure.

a2a1

B

m

17. See the diagram, The system is in equilibrium. There is no

friction anywhere. Spring, string, pulley are massless. Find

spring compression.m

M

k

q

18. Blocks are connected by inextensible strings as shown in the figure. Contactsurfaces are frictionless. Determine acceleration of each block, when thesystem is released from rest .

5kg

3kg

3kg

19. Assuming all surfaces to be smooth. Minimum valueof a so that sphere looses contact at P is

(A) g sin a (B) g tan a(C) g cot a (D) g cosec a

a a

P a

20. A ball of mass m is hanging from a uniform rope of mass M and length L whoseone end is connected to the ceiling of an elevator as shown in the figure. If the

elevator has a uniform acceleration of a m/s2upward, find the tension in the rope

as a function of x. What is the force exerted by the rope on the ceiling?m

L

a

x


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Assignment

FIITJEE

FIITJEE

ANSWERS (LAWS OF MOTION)

1. C 2. B 3 B 4. A

5. D 6. C 7. B 8. C

9. B 10. C 11. A,B,C,D 12. B,C,D

13. D 14. D 15. C 16. a2= 6a1

17.k

sinmg q.

18 a1= 5.3 m/s2, a2= 0.71 m/s

2, a3= 6.79 m/s

2.

19. B

20. (a + g)(m + M); M (a + g) downward

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