Subject Experts Solutions for Exercise 2: PRACTICE QUESTIONS (COMPETITION WING)

If the spring balance graded in gravitational units (CGS system) shows $20$ as the reading, then the mass of the body is _____ $\mathrm{kg}$.

Why would any small object coming from space catches fire after entering into the Earth's atmosphere?

The force exerted on a moving bike by its engine is $180 \mathrm{N}$ and the roughness of the road applies a retarding force of $5 \mathrm{N}$on its tyres. Find the force that accelerates the vehicle and also mention the type of friction involved here.

Ammu, a second-class student of mass $15 \mathrm{kg}$ is sliding over a slide inclined at an angle of $30°$ but her motion stopped at the middle of the slide. What would be the reason for this?

An iron cylinder of base area $7 {\mathrm{cm}}^2$ and mass $10 \mathrm{kg}$ is melted and reshaped into a rod of area of cross-section $1 {\mathrm{cm}}^2$. Calculate the increase in the pressure exerted on a plane surface when both the cylinder and the rod are made to stand vertically on a plane surface. $\left(g=10 \mathrm{m} {\mathrm{s}}^{-2}\right)$

A girl can move a stone block at rest, placed on an iron sheet, by applying a force of $60 \mathrm{N}$. The force reduced to one-third when an oil is applied on the iron sheet. How much force will be required to move a stone block in second case?

Six helium balloons can lift a teddy bear of weight $50 \mathrm{N}$. If the radius of each helium balloon is $2\mathrm{\pi }$, calculate the pressure inside each balloon.

A silver cube of base area of $30 {\mathrm{m}}^2$and mass $2 \mathrm{kg}$ is melted and changed into a cuboid of area of cross section $2 {\mathrm{m}}^2$. Calculate, how much pressure is increased on a plane surface when both the cube and cuboid made vertically stand.