Laws of Motion · Question 71

A box of mass 15 kg is kept on the floor of a stationary trolley. The coefficient of static friction between the box and the trolley is 0.12. Keeping the box in stationary state over the trolley, the maximum acceleration with which the trolley can be moved horizontally in m s-2 is : (g = 10 m/s2)

1. 1.8
2. 1.2
3. 1.5
4. 2.1

The magnitude and direction of the acceleration produced in a body of mass 5 kg when two mutually perpendicular forces 8 N and 6 N act on it, are respectively :

1. 2 m s-2; -1(3/4) with 8 N force
2. 2 m s-2; -1(4/3) with 8 N force
3. 2 m s-2; -1(3/4) with 6 N force
4. 20 m s-2; -1(4/3) with 8 N force

A car travels on a circular racetrack of radius 50 m, which is banked at an angle . If the car travels at a speed 10 ms-1, then the wear and tear on its tyres is minimum. Taking the acceleration due to gravity to be 10 ms-2, the value of is:

1. -1(2 3)
2. -1 ( 15 )
3. -1 ( 25 )
4. -1( 3/2)

A frictionless circular wire of unit radius is fixed on the horizontal plane. Two-point particles of unit mass start moving simultaneously from point A ( = 2 ) with identical uniform angular speeds in opposite directions, and meet again at point B ( = - 2 ). During this time, which of the following figures schematically represent the magnitude of the total linear momentum P of the system, as a function of ? [figure]

1. [figure]
2. [figure]
3. [figure]
4. [figure]

A ball of mass 0.5 kg is dropped from a height of 40 m. The ball hits the ground and rises to a height of 10 m. The impulse imparted to the ball during its collision with the ground is (Take g = 9.8 m/s2)

1. 0
2. 84 N s
3. 21 N s
4. 7 N s

There are two inclined surfaces of equal length (L) and same angle of inclination 45 with the horizontal. One of them is rough and the other is perfectly smooth. A given body takes 2 times as much time to slide down on rough surface than on the smooth surface. The coefficient of kinetic friction ( k) between the object and the rough surface is close to

1. 0.5
2. 0.75
3. 0.25
4. 0.40

A horizontal force 10 N is applied to a block A as shown in figure. The mass of blocks A and B are 2 kg and 3 kg respectively. The blocks slide over a frictionless surface. The force exerted by block A on block B is : [figure]

1. Zero
2. 4 N
3. 6 N
4. 10 N

A bob is whirled in a horizontal plane by means of a string with an initial speed of rpm. The tension in the string is T. If speed becomes 2 while keeping the same radius, the tension in the string becomes:

1. T
2. 4T
3. T4
4. 2T

A bob is whirled in a horizontal circle by means of a string at an initial speed of 10 rpm. If the tension in the string is quadrupled while keeping the radius constant, the new speed is:

1. 20 rpm
2. 40 rpm
3. 5 rpm
4. 10 rpm

A box of mass 5 kg is pulled by a cord, up along a frictionless plane inclined at 30 with the horizontal. The tension in the cord is 30 N. The acceleration of the box is (Take g = 10 m s-2)

1. 2 m s-2
2. Zero
3. 0.1 m s-2
4. 1 m s-2