Question & Answer

A circle touches the x­-axis and also touches the circle with centre at (0, 3) and radius 2. What will be the locus of the centre of the circle?

A particle of mass 4 m which is at rest explodes into three fragments, two of the fragments each of mass m are found to move each with a speed v making an angle 90 with each other. The total energy relased in this explosion is -

A slow moving electron collides elastically with a hydrogen atom at rest. The initial and final motions are along the same straight line. What fraction of electron's kinetic energy is transferred to the hydrogen atom? The mass of hydrogen atom is 1850 times the mass of electron?

If the circles x² + y² + 2ax + cy + a = 0 and x² + y² – 3ax + dy – 1 = 0 intersect in two distinct points P and Q then the line 5x+by – a = 0 passes through P and Q for

If a vertex of a triangle is (1, 1) and the midpoints of two sides through this vertex are (–1, 2) and (3, 2), then what will be the centroid of the triangle.

If non ­zero numbers a, b, c are in H.P., then the straight line  always passes through a fixed point. That point is

The line parallel to thex­axis and passing through the intersection of the lines ax + 2by + 3b = 0 and bx – 2ay – 3a = 0, where (a, b)  (0, 0) is

Let P be the point (1, 0) and Q a point on the locus y2 = 8x. The locus of midpoint of PQ is

The mass of a rocket is 500 kg and the relative velocity of the gases ejecting from it is 250 m/s with respect to the rocket. The rate of burning of the fuel in order to give the rocket an initial acceleration 20 m/s2 in the vertically upward direction (g = 10 m/s2), will be

A 20 g bullet pierces through a plate of mass m1 = 1 kg and then comes to rest inside a second plate of mass m2 = 2.98 kg. It is found that the two plates, initially at rest, now move with equal velocities. The percentage loss in the initial velocity of bullet when it is between m1 and m2. (Neglect any loss of material of the bodies, due to action of bullet.) will be

If the straight lines x = 1 + s, y = –3  z = 1 +  and x = t/2, y = 1 + t, z = 2 – t, with parameters s and t respectively, are co­planar, then  equals

A bullet of mass 10g travelling horizontally with a velocity of 300 m/s strikes a block of wood of mass 290 g which rests on a rough horizontal floor. After impact the block and the bullet move together and come to rest when the block has travelled a distance of 15 m. The coefficient of friction between the block and the floor will be - (Duration of impact is very short)

The eccentricity of an ellipse, with its centre at the origin, is 1/2. If one of the directrices is x = 4, then the equation of the ellipse is

The intercept on the line y = x by the circle x² + y² – 2x = 0 is AB. Equation of the circle on AB as diameter is

If the lines 2x + 3y + 1 = 0 and 3x – y – 4 = 0 lie along diameters of a circle of circumference  then the equation of the circle is

If a  0 and the line 2bx + 3cy + 4d = 0 passes through the points of intersection of the parabolas y2 = 4ax and x2 = 4ay, then

A variable circle passes through the fixed point A(p, q) and touches x­-axis. The locus of the other end of the diameter through A is

If a circle passes through the point (a, b) and cuts the circle x² + y² = 4 orthogonally, then the locus of its centre is

If the sum of the slopes of the lines given by x² – 2cxy – 7y² = 0 is four times their product, then c has the value

The equation of the straight line passing through the point (4, 3) and making intercepts on the co­ ordinate axes whose sum is –1 is

Let A(2, –3) and B(–2, 1) be vertices of a triangle ABC. If the centroid of this triangle moves on the line 2x + 3y = 1, then the locus of the vertex C is the line

The normal to the curve x = a(1 + cos), y = asin at  always passes through the fixed point

A point on the parabola y² = 18x at which the ordinate increases at twice the rate of the abscissa is

The centre of the circle passing through (0, 0) and (1, 0) and touching the circle x² + y² = 9 is

Locus of mid point of the portion between the axes of  where p is constant is

The point of lines represented by 3ax² + 5xy + (a – 2)y² = 0 and ^ to each other for

The centres of a set of circles, each of radius 3, lie on the circle x² + y² = 25. The locus of any point in the set is

Locus of the centroid of the triangle whose vertices are (a cost, a sint), (b sint, –b cost) and (1, 0), where t is a parameter, is

A rifle man,who together with his rifle has a mass of 100 kg, stands on a smooth surface fires 10 shots horizontally. Each bullet has a mass 10 gm and a muzzle velocity of 800 m/s. What velocity does rifle man acquire at the end of 10 shots

A uniform rod of length 4 m and mass 20 kg is lying horizontal on the ground. The work done in keeping it vertical with one of its ends touching the ground, will be

If the pairs of straight lines x² – 2pxy – y² = 0 and x² – 2qxy – y² = 0 be such that each pair bisects the angle between the other pair, then

The work done by a person in carrying a box of mass 10 kg through a vertical height of 10 m is 4900 J. The mass of the person is

A particle of mass m is moving in a horizontal circle of radius r, under a centripetal force equal to (–k/r2), where k
is a constant. The total energy of the particle is

A bus of mass 1000 kg has an engine which produces a constant power of 50 kW. If the resistance to motion, assumed constant is 1000 N. The maximum speed at which the bus can travel on level road and the acceleration when it is travelling at 25 m/s, will respectively be?

A uniform chain is held on a frictionless table with one- fifth of its length hanging over the edge. If the chain has a length l and a mass m, how much work is required to pull the hanging part back on the table ?

A boy pulls a 5 kg block 20 metres along a horizontal sur- face at a constant speed with a force directed 45° above the horizontal. If the coefficient of kinetic friction is 0.20, how much work does the boy do on the block?

A square of side a lies above the x ­axis and has one vertex at the origin. The side passing through the origin makes an angle  with the positive direction of the x-­axis. The equation of its diagonal not passing through the origin is

The lines 2x – 3y= 5 and 3x – 4y= 7 are diameters of a circle having area as 154 sq. units. Then the equation of the circle is

If the two circles (x – 1)² + (y – 3)² = r² and x² + y² – 8x + 2y + 8 = 0 intersect in two distinct points, then

The normal at the point (bt₁², 2bt₁) on a parabola meets the parabola again in the point (bt₂², 2bt₂), then

The foci of the ellipse  and the hyperbola  coincide. Then the value of b² is

A triangle with vertices (4, 0), (–1, –1), (3, 5) is

The equation of a circle with origin as a center and passing through equilateral triangle whose median is of length 3a is

 A chain of linear density 3 kg /m and length 8 m is lying on the table with 4 m of chain hanging from the edge. The work done in lifting the chain on the table will be ?

An automobile of mass m accelerates from rest. If the engine supplies a constant power P, the velocity at time t is given by

A force F =(7–2x+3x*x )N is applied on a 2kg mass which displaces it from x = 0 to x = 5 m. Work done in joule is ?

The work done in pulling a body of mass 5 kg along an inclined plane (angle 60) with coefficient of friction 0.2 through 2 m,will be?

A body is acted upon by a force F=-i+2j+3k.The work done by the force in displacing it from (0,0,0) to (0,0,4m) will be?