Physics-DPP-2-law of motion
PHYSICS Topic: LAWS OF MOTION Date:
1. An elevator and its load have a total mass of 800 kg. If the elevator, originally moving downward at 10 m/s, is brought to rest with constant deceleration in a distance of 25 m, the tension in the supporting cable will be : (g = 10 m/s2) :
(a) 8000 N (b) 6400 N (c) 12200 N (d) 9600 N
2. A block of weight 5 N is pushed against a vertical wall by a force 12 N. The coefficient of friction between the wall and block is 0.6. The magnitude of the force exerted by the wall on the block is :
(a) 12 N (b) 5 N (c) 7.2 N (d) 13 N
3. The acceleration of the 2 kg block, if the free end of string is pulled with a force of 20 N as shown is :
(a) zero (b) 10 m/s2 (c) 5 m/s2 (d) 6 m/s2
4. Two blocks, each having a mass M, rest on frictionless surfaces as shown in the figure. If the pulleys are light and frictionless, and M on the incline is allowed to move down, then the tension in the string will be :
(a) 2 Mg sin θ
3
(b) 3 Mgsinθ 2
(c) Mg sin θ
2
(d) 2 Mg sin θ
5. In the shown figure the tension in the upper string immediately after lower string is cut is
(a) mg (b) 2 mg
(c) 3 mg (d) 3 mg
2
6. In the 5th question the acceleration (in m/s2) of block A & B just after lower string is cut are
(a) 0,g ¯ (b) g g ¯ (c) g ¯ g ¯ (d) g g
PHYSICS Topic: LAWS OF MOTION Date:
7. A smooth inclined plane of length L, having an inclination θ with horizontal is inside a lift which is moving down with retardation
a. The time taken by a block to slide down the inclined plane from rest will be :
(a)
(b)
(c)
(d)
8. Three blocks are placed at rest on a smooth inclined plane with force acting on m1 parallel to the inclined plane. Find the contact froce betweem m2 and m3.
(a) (m1 + m2 + m3 )F
(b)
m3F
(c) F – (m
+ m )g
(d) None of the above
m1 + m2 + m3 1 2
3
9. In this figure how much force on mass m = 5kg should be applied, so that it just won’t slip. Given that car is moving with constant acceleration a = 5 m/s2.
(a) 170 N (b) 180 N (c) 150 N (d) 250 N
10. All surfaces shown in figure are smooth. System is released with the spring unstretched. In equilibrium, compression in the spring will be :
mg
(a)
(b)
2mg
k (c)
(M +
m)g
mg
(d) k
PHYSICS Topic: LAWS OF MOTION Date:
Answer Key
1. (d) 2. (d) 3. (b) 4. (c) 5. (c)
6. (b)
7. (d)
8. (b)
9.
(c)
10. (d)
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