Swimming is possible on account of 

  • First law of motion

  • Second law of motion

  • Third law of motion

  • Newton's law of gravitation

On a stationary sailboat, the air is blown at the sails from a fan attached to the boat. The boat will:

  • remain stationary

  • spin around

  • move in a direction opposite to that in which air is blown

  • move in the direction in which the air is blown

A man is standing at a spring platform. Reading of spring balance is 60 kg-wt. If a man jumps outside the platform, then reading of spring balance:

  • first increases then decrease to zero.

  • decreases.

  • increases.

  • remains same.

A body of mass 5 kg is suspended by a spring balance on a smooth inclined plane as shown in the figure. The spring balance measure:

  • 50 N

  • 25 N

  • 500 N

  • 10 N

The elevator is ascending. Together, the lift and the passenger weigh 1500 kg. The variation in the speed of the lift is as given in the graph. The tension in the rope pulling the lift at t = 11th sec will be:

     

  • 17400 N

  • 14700 N

  • 12000 N

  • Zero

A player caught a cricket ball of mass 150 gm moving at a rate of 20 m/s. If the catching process be completed in 0.1 s, then the force of the blow exerted by the ball on the hands of the player is 

  • 0.3 N

  • 30 N

  • 300 N

  • 3000 N

A rocket has a mass of 100 kg. 90% of this is fuel. It ejects fuel vapours at the rate of 1 kg/sec with a velocity of 500 m/sec relative to the rocket. It is supposed that the rocket is outside the gravitational field. The initial upthrust on the rocket when it just starts moving upwards is:

  • Zero

  • 500 N

  • 1000 N

  • 2000 N

In which of the following cases, a force will not be required to keep the:

  • particle going in a circle.

  • particle going along a straight line.

  • momentum of the particle constant.

  • acceleration of the particle constant.

A ball of mass 150g starts moving with an acceleration of 20 m/s2 when hit by a force, which acts on it for 0.1 sec. The impulsive force is:

  • 0.5 N-s

  • 0.1 N-s

  • 0.3 N-s

  • 1.2 N-s

A body, whose momentum is constant, must have a constant: 

  • force.

  • velocity.

  • acceleration.

  • All of these

Rocket engines lift a rocket from the earth surface because hot gases with high velocity:

  • push against the earth.

  • push against the air.

  • react against the rocket and push it up.

  • heat up the air which lifts the rocket.

A force of 50 dynes is acted on a body of mass 5 g which is at rest for an interval of 3 seconds, then impulse is 

  • 0.15×10−3 Ns

  • 0.98×10−3 Ns

  • 1.5×10−3 Ns

  • 2.5×10−3 Ns

Three forces starts acting simultaneously on a particle moving with velocity v→. These forces are represented in magnitude and direction by the three sides of a triangle ABC (as shown). The particle will now move with velocity 

  • v→ remaining unchanged

  • Less than v→

  • Greater than v→

  • v→ in the direction of the largest force BC

Two blocks are connected by a string as shown in the diagram. The upper block is hung by another string. A force F applied on the upper string produces an acceleration of 2 m/s2 in the upward direction in both the blocks. If T and T’ be the tensions in the two parts of the string, then 

  • T = 70.8 N and T’ = 47.2 N

  • T = 58.8 N and T’ = 47.2 N

  • T = 70.8 N and T’ = 58.8 N

  • T = 70.8 N and T’ = 40.2 N

A block is kept on a frictionless inclined surface with an angle of inclination 'α'. The incline is given an acceleration 'a' to keep the block stationary. Then a is equal to 

  • g

  • gtanα

  • g/tanα

  • gcosecα

A block of mass M is pulled along a horizontal frictionless surface by a rope of mass m. If a force P is applied at the free end of the rope, the force exerted by the rope on the block will be: 

  • P

  • PmM+m

  • PMM+m

  • PmM−m

Three equal weights A, B and C of mass 2 kg each are hanging on a string passing over a fixed frictionless pulley as shown in the figure The tension in the string connecting weights B and C is 

  • Zero

  • 13 N

  • 3.3 N

  • 19.6 N

Two masses of 4 kg and 5 kg are connected by a string passing through a frictionless pulley and are kept on a frictionless table as shown in the figure. The acceleration of 5 kg mass is

  • 49 m/s2

  • 5.44 m/s2

  • 19.5 m/s2

  • 2.72 m/s2

Two masses 2 kg and 3 kg are attached to the end of the string passed over a pulley fixed at the top. The tension and acceleration are

  • 7g8; g8

  • 21g8; g8

  • 21g8; g5

  • 12g5; g5

Three blocks A, B and C weighing 1, 8 and 27 kg respectively are connected as shown in the figure with an inextensible string and are moving on a smooth surface. T3 is equal to 36 N. Then T2 is 

  • 18 N

  • 9 N

  • 3.375 N

  • 1.25 N

Two bodies of mass 3 kg and 4 kg are suspended at the ends of massless string passing over a frictionless pulley. The acceleration of the system is (g = 9.8 m/s2) 

  • 4.9 m/s2

  • 2.45 m/s2

  • 1.4 m/s2

  • 9.5 m/s2

Three solids of masses m1, m2 and m3 are connected with weightless string in succession and are placed on a frictionless table. If the mass m3 is dragged with a force T, the tension in the string between m2 and m3 is 

  • m2m1+m2+m3T

  • m3m1+m2+m3T

  • m1+m2m1+m2+m3T

  • m2+m3m1+m2+m3T

Three blocks of masses m1, m2 and m3 are connected by massless strings as shown on a frictionless table. They are pulled with a force T3 = 40 N. If m1 = 10 kg, m2 = 6 kg and m3 4 kg, the tension T2 will be 

  • 20 N

  • 40 N

  • 10 N

  • 32 N

A light string passes over a frictionless pulley. To one of its ends a mass of 6 kg is attached. To its other end a mass of 10 kg is attached. The tension in the thread will be 

  • 24.5 N

  • 2.45 N

  • 79 N

  • 73.5 N

Two masses of 5kg and 10kg are connected to a pulley as shown. What will be the acceleration of the system (g = acceleration due to gravity)

  • g

  • g2

  • g3

  • g4

A block A of mass 7 kg is placed on a frictionless table. A thread tied to it passes over a frictionless pulley and carries a body B of mass 3 kg at the other end. The acceleration of the system is (given g = 10 ms–2) 

  • 100 ms–2

  • 3 ms–2

  • 10 ms–2

  • 30 ms–2

Three blocks of masses 2 kg, 3 kg and 5 kg are connected to each other with light string and are then placed on a frictionless surface as shown in the figure. The system is pulled by a force F = 10 N, then tension T1 = 

  • 1N

  • 5 N

  • 8 N

  • 10 N

A body of weight 2kg is suspended as shown in the figure. The tension T1 in the horizontal string (in kg wt) is 

  • 2/3

  • 3/2

  • 23

  • 2

One end of a massless rope, which passes over a massless and frictionless pulley P is tied to a hook C while the other end is free. Maximum tension that the rope can bear is 360 N. with what value of minimum safe acceleration (in ms–2) can a monkey of 60 kg move down on the rope 

  • 16

  • 6

  • 4

  • 8

A light string passing over a smooth light pulley connects two blocks of masses m1 and m2 (vertically). If the acceleration of the system is g/8 then the ratio of the masses is 

  • 8 : 1

  • 9 : 7

  • 4 : 3

  • 5 : 3

0:0:1


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