A block of mass 200 kg is being pulled up by men on an inclined plane at angle of 45° as shown in the figure. The coefficient of static friction is 0.5. Each man can only apply a maximum force of 500 N. Calculate the number of men required for the block to just start moving up the plane
 

1) 10
2) 15
3) 5 
4) 3

The mass of a hydrogen molecule is $$3.32 \times 10^{-27} \, kg$$. If $$10^{23}$$ hydrogen molecules strike, per second,a fixed wall of area $$ 2 \, cm^2$$ at an angle of $$45^{\circ} $$ to the normal, and rebound elastically with a speed of $$10^3 \, m/s$$ , then the pressure on the wall is nearly :

1) $$2.35 \times 10^3 \, N/m^2$$
2) $$4.70 \times 10^3 \, N/m^2$$
3) $$2.35 \times 10^2 \, N/m^2$$
4) $$4.70 \times 10^2 \, N/m^2$$

Energy required for the electron excitation in Li from the first to the third Bohr orbit is

1) 36.3 eV
2) 108.8 eV
3) 122.4 eV
4) 12.1 eV

An iron sphere of mass 20 × 10^-3 kg falls through a viscous liquid with terminal velocity 0.5 ms^-1 . The terminal velocity (in ms^-1) of another iron sphere of mass 54 × 10^-2 kg is

1) 4.5
2) 3.5
3) 2.5
4) 1.5

Two similar open organ pipes when sounded together produce 7 beats/s. If their lengths are in the ratio 50 : 51 then ratio of their frequencies will be

1) 7 :1
2) 50 : 51
3) 51 : 50
4)  1 : 7

Young’s double slit experiment is carried out by using green,red and blue light, one colour at a time. The fringe widths recorded are β_G, β_R and β_B respectively then,

1) β _G > β_B > β_R
2) β_B > β_G > β_R
3) β_R > β_B > β_G
4) β_R > β_G > β_B

 A meter stick is supported at each end by a spring scale. A heavy mass is then hung on the meter stick so that the spring scale on the left hand side reads four times the value of the spring scale on the right hand side. If the mass of the meter stick is negligible compared to the hanging mass, how far from the right hand side is the large mass hanging?

1) 25 cm
2) 50 cm
3) 67 cm
4) 80 cm

 The person in the drawing is standing on crutches. Assume that the force exerted on each crutch by the ground is directed along the crutch. If the coefficient of static friction between a crutch and the ground is 0.90, determine the largest angle θ^MAX that the crutch can have just before it begins to slip on the floor. 

1) tan^–1 (0.9)   2) cot^–1  (0.9)    3) sin^–1  (0.9)   4) cos^–1  (0.9)

Two identical lights sources S1  and S2 emit the light of same wavelength λ. These light rays will exhibit interference if 

1) their phase difference remain constant
2) their phase difference is distributed randomly
3) their light intensities remain constant.
4) their light intensities change continuously

The height at which the weight of a body becomes 1/16 th its weight on the surface of (radius R) is

1) 4R
2) 3R
3) 15R
4) 5R