11.  are two vectors and θ is the angle between them if  the value of θ is:

• 60^o

• 45^o

• 30^o

• 30^o

A particle moving along x- axis has acceleration f, at time t, given f = f_o (1-t/T), where f_o and T are constants. The particle at t =0 and the instant when f = 0, the particle's velocity (v_x) is:

• f_oT

• f_oT²/2

• f_oT²

• f_oT²

If the cold junction of a thermocouple is kept at 0^o C and the hot junction is kept at T^o C, then the relation between neutral temperature (T_n) and temperature of inversion (T_i) is:

• 

• T_n = 2T_i

• T_n = T_i -T

• T_n = T_i -T

Nickel shows the ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show:

• paramagnetism

• anti -ferromagnetism

• no magnetic property

• no magnetic property

A particle executes simple harmonic oscillation with an amplitude a. The period of oscillation is T. The minimum time taken by the particle to travel half of the amplitude from the equilibrium position is:

• T/4

• T/8

• T/12

• T/12

The particle executing simple harmonic motion has a kinetic energy K_o cos² ωt. The maximum values of the potential energy and the toatal energy are respectively:

• 0 and 2K_o

• K_o/2 and K₀

• K_o and 2K_o

• K_o and 2K_o

A mass of 2.0 Kg is put on a flat pan attached to a vertical spring fixed on the ground as shown in the figure. The mass of the spring and the pan is negligible. When pressed slightly and released the mass executes a simple harmonic motion. The spring constant is 200 N/m. What should be the minimum amplitude of the motion, so that the mass gets detached from the pan?

Take g = `10 m/s²

• 8.0 cm

• 10.0 cm

• any value less than 12.0 cm

• any value less than 12.0 cm

A black body is at 727^o C. It emits energy at a rate which is proportional to:

• (727)²

• (1000)⁴

• (1000)²

• (1000)²

An engine has an efficiency of 1/6. When the temperature of sink is reduced by 62^o C, its efficiency is doubled. The temperature of the source is:

• 124^o C

• 37^o C

• 62^o C

• 62^o C

For a cubic structure which one of the following relations indicating the cell characteristic is correct?