A car of mass 1000 kg moves on a circular track with a radius of 40 m. If the coefficient of friction is 1.28, the maximum velocity with which the car can be moved is:
1. $22.4~\text{m/s}$
2. $112~\text{m/s}$
3. $\frac{0.64\times40}{1000\times100}~\text{m/s}$
4. $1000~\text{m/s}$

Light travels faster in the air than in glass. This is in accordance with:

The speed of airflow on the upper and lower surfaces of a wing of an aeroplane is $v_1$ and $v_2$ respectively. If $A$ is the cross-section area of the wing and $\rho$ is the density of air, then the upward lift is:
1. $\frac12\rho A(v_2-v_2)$
2. $\frac12\rho A(v_1+v_2)$
3. $\frac12\rho A(v_1~^2-v_2~^2)$
4. $\frac12\rho Av_1~^2+v_2~^2$

A parallel plate condenser is filled with two dielectrics as shown in the figure. The area of each plate is $A~\text m^2$ and the separation is $d$ meter. The dielectric constants are $K_1$ and $K_2$ respectively. Its capacitance in farad will be: 
             

1. $\frac{2\varepsilon_{_0}A}{d}\Big(\frac{K_1+K_2}{K_1K_2}\Big)$
2. $\frac{2\varepsilon_{_0}A}{d}\Big(\frac{K_1K_2}{K_1+K_2}\Big)$
3. $\frac{\varepsilon_{_0}A}{d}\Big(\frac{K_1+K_2}{2K_1K_2}\Big)$
4. $\frac{\varepsilon_{_0}AK_1K_2}{2(d_2K_1+d_1K_2)}$