If the lattice parameter for a crystalline structure is 3.6 A, then atomic radius in fcc crystal is

• 1.18 A

• 2.10 A

• 2.92 A

• 1.27 A

If the error in the measurement of radius of sphere is 2%, then the error in the determination of volume of the sphere will be

• 4%

• 6%

• 8%

• 2%

B.

6%

 

A roller coaster is designed such that riders experience " weightlessness" as they go round the top of a hill whose radius of curvature is 20 m.  The speed of the car at the top of the hill is between

• 14 m/s and 15 m/s

• 15m/s and 16 m/s

• 16 m/s and 17 m/s

• 13m/s and 17 m/s

A.

14 m/s and 15 m/s

Balancing the forces, we get
Mg-N = Mv²/R
For weightlessness, N = 0 
therefore, MV²/R = Mg
where R is the radius of curvature and v is the speeds of the car.
Therefore,

Thus, the speed of the car at the top of the hill is between 14 m/s and 15 m/s

The ratio of the radii of gyration of a circular disc to that of a circular ring, each of same mass and radius, around their respective axes is 

• 
• 
• 
• 

B.

The square root of the ratio of the moment of inertia of rigid body nad its mass is called radius of gyration.
As in key idea, radius of gyration is given by

Water falls from a height of 60 m at the rate of 15 kg /s to operate a turbine. The losses due to frictional 

• 8.1 kW

• 10.2 kW

• 12.3 kW

• 7.0 kW