A block of mass m is in contact with the cart C as shown in the figure


The coefficient of static friction between the block and the cart is μ. The acceleration α of the cart that will prevent the block from falling satisfies

A circular disk of moment of inertia I_t is rotating in a horizontal plane, about its symmetry axis, with a constant angular speed. Another disk of moment of inertia I_b is dropped coaxially onto the rotating disk. Initially, the second disk has zero angular speed. Eventually, both the disks rotate with constant angular speed.The energy lost by the initially rotating disc due to friction is 

3.

The radii of circular orbits of two satellites A and B of the earth are 4R and R, respectively. If the speed of satellite A is 3v. then the speed of satellite B will be

• 3v/4

• 6v

• 12 v

• 12 v

A ball is dropped from  a high-rise platform at t=0 starting from rest. After 6s another ball is thrown downwards from the same platform with a speed v. The two balls meet at t= 18s. What is the value of v? (take g= 10 ms^-2)

• 74 ms^-2

• 55 ms^-1

• 40 ms^-1

• 40 ms^-1

A ball moving with velocity 2 ms^-1 collides head on with another stationary ball of double the mass. If the coefficient of restitution is 0.5, then their velocities (in ms^-1) after collision will be

• 0,1

• 1,1

• 1,0.5

• 1,0.5

A Particle has initial velocity and has acceleration. Its speed after 10s is

• 7 unit

•  unit

• 8.5 unit

• 8.5 unit

An engine pumps water through a hosepipe. Water passes through the pipe and leaves it with a velocity of 2 ms^-1. The mass per unit length of water in the pipe is 100 kgm^-1. What is the power of the engine?

• 400 W

• 200 W

• 100 W

• 100 W

Which one of the following bonds produces a solid that reflects light in the visible region and whose electrical conductivity decreases with temperature and hs high melting point?

• metallic bonding

• van der Waal's bonding

• Ionic bonding

• Ionic bonding

A particle moves a distance x in time t according to equation x  = (t +5)^-1. The acceleration of particle is proportional to

• (velocity)^3/2

• (distance)²

• (distance)^-2

• (distance)^-2

Two particles which are initially at rest, move towards each other under the action of their internal attraction. If their speeds are v and 2v at any instant, then the speed of centre of mass of the system will be

• 2v

• 0

• 1.5 v

• 1.5 v