Two identical charged spheres are suspended by strings of equal lengths. The strings make an angle of $45^{\circ}$ with each other. When the system is immersed in a liquid of relative density 0.8 , the angle between the strings remains unchanged. If the density of the material of the sphere is $2.4 \mathrm{gcm}^{-3}$, what is the dielectric constant of the liquid?
1.6
1.5
0.5
2
A car, starting from rest, accelerates at a rate of $\beta$ through a distance S , then continues at constant speed for time t and then decelerates at a rate of $\frac{\beta}{2}$ to come to rest. If the total distance travelled is $10 S$, then ratio $\frac{S}{t^2}$ is
$\frac{2 \beta}{19}$
$\frac{2 \beta}{49}$
$\frac{\beta}{49}$
$\frac{2 \beta}{64}$
A glass slab of 16 cm thickness has its bottom surface silvered. An air bubble is located inside the glass slab at a distance of 8 cm from the top surface. The refractive index of glass is 1.6 . Which of the following correctly represents the number of images seen by an observer looking vertically downwards from air onto the top surface?
A. Only one image is seen at a depth of 5 cm
B. Multiple images are formed due to multiple reflections and refractions
C. Only one image is seen at a depth of 16 cm
D. Two images are seen at depths 5 cm and 15 cm
B
C
D
A
A body is projected vertically upwards from the surface of earth with a velocity ' $v$ ' to reach a height of $10 R$, where $R$ is the radius of the earth, then $v$ is
$\sqrt{\frac{21 \mathrm{gR}}{10}}$
$\sqrt{\frac{21 \mathrm{gR}}{11}}$
$\sqrt{\frac{20 \mathrm{gR}}{11}}$
$\sqrt{\frac{10 \mathrm{gR}}{11}}$
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