Physics Test - 49

Materials that do not transfer mechanical energy well. These tend to be soft,flexible, low density, and with high surface area to linear area ratios.

Erg cross Sec is the unit ofPlanck's constant.

A vector quantity is a quantity which has both magnitude and direction. Here in the given options, speed is a scalar quantity but not the vector quantity.

Total internal reflection can take place when light travels from diamond to glass.

When a ray of light travels from a denser medium to a rarer medium, then the total internal reflection of light occurs provided that the angle of incidence is greater than the critical angle of the medium interface.

The refractive index of diamond is 2.42 and that of glass is 1.5, thus total internal reflection can occur if light travels from diamond to glass.

Let \(^{\prime} \mathrm{t}_{\mathrm{a}}^{\prime}\) be time of ascent and \(^{\prime} \mathrm{t}_{\mathrm{d}}^{\prime}\) be time of descent.

\(^{\prime} \mathrm{a}^{\prime}\) is the retardation due to air resistance (opposite to direction of motion of body).

\( \mathrm{g}^{\prime}\) is acceleration due to gravity (vertically downwards always).

When object is thrown upwards:

Total acceleration \(=(\mathrm{a}+\mathrm{g})\)

\(\mathrm{t}_{\mathrm{a}}=\frac{\mathrm{u}}{(\mathrm{a}+\mathrm{g})} \quad[\mathrm{u} \rightarrow\) velocity of object \(]\)

'a' and ' \(\mathrm{g}\) ' acts vertically downwards.

When object is falling down:

Total acceleration \(=(\mathrm{g}-\mathrm{a})\)

\(\mathrm{t}_{\mathrm{d}}=\frac{\mathrm{u}}{(\mathrm{g}-\mathrm{a})}\)

'g' acts downwards and 'a' acts vertically upwards.

Since \((\mathrm{g}+\mathrm{a})\) is greater than \((\mathrm{g}-\mathrm{a})\), so \(t_{d}>t_{a}\) because greater the denominator, lesser the value of fraction.

Therefore,

Time of ascent \(<\) Time of descent

Centrifugation is a separation process which uses the action of centrifugal force to promote accelerated settling of particles in a solid-liquid mixture.

The washing machine consists of centrifuge for this purpose. A centrifuge is a piece of equipment that puts an object in rotation around a fixed axis, applying a force perpendicular to the axis of spin that can be very strong.

One astronomical unit is the average distance betweenEarth and the Sun.

Pascalis the SI unit of pressure.

If lift is going up with acceleration, the apparent weight of a body ismore than the true weight.

The property of matter to increase in size on heating is called thermal expansion.

As we know, any particle or object that occupies space and has some mass is called matter. Thermal expansion is the change in the size of an object as its temperature changes. Also, we know that thermal expansion is defined as the tendency of the matter to change its shape, area, volume, and density in response to the change in temperature. Thermal expansion generally does not include phase transitions.

Therefore, thermal expansion is the property of matter to increase in size on heating.