CBSE Syllabus for Class 8 Maths 2024 - Download PDF

A boy standing on a stationary lift (open from above) throws a ball upwards with the maximum initial speed he can, equal to 49 m s-1. How much time does the ball take to return to his hands? If the lift starts moving up with a uniform speed of 5 m s-1 and the boy again throws the ball up with the maximum speed he can, how long does the ball take to return to his hands?

A player throws a ball upwards with an initial speed of 29.4ms ?1 . (a) What is the direction of acceleration during the upward motion of the ball ? (b) What are the velocity and acceleration of the ball at the highest point of its motion ? (c) Choose x = 0 m and t = 0 s to be the location and time of the ball at its highest point, vertically downward direction to be the positive direction of x-axis, and give the signs of position, velocity and acceleration of the ball during its upward, and downward motion. (d) To what height does the ball rise and after how long does the ball return to the players hands ? (Take g=9.8m/s 2 and neglect air resistance).

Choose the correct statement of the following a. conversion of solid into vapours without passing through the liquid state is called vapourisation. b. conversion of vapours into solid without passing through the liquid state is called sublimation. c. conversion of vapours into solid without passing through the liquid state is called freezing. d. conversion of solid into liquid is called sublimation.

Fill in the blanks: a. Evaporation of a liquid at room temperature leads to a __________ effect. b. At room temperature the forces of attraction between the particles of solid substances are __________ than those which exist in the gaseous state. c. The arrangement of particles is less ordered in the _________ state. However, there is no order in the _______ state. d. _____________ is the change of gaseous state directly to solid state without going through the _____________ state. e. The phenomenon of change of a liquid into the gaseous state at any temperature below its boiling point is called ___________.

For the following statements, write T for True and F for False. (a) J.J. Thomson proposed that the nucleus of an atom contains only nucleons. (b) A neutron is formed by an electron and a proton combining together. Therefore, it is neutral. (c) The mass of an electron is about 1/2000 times that of proton. (d) An isotope of iodine is used for making tincture iodine, which is used as a medicine.

General electronic configuration of outermost and penultimate shell of an atom is (n-1)s^{2} (n-1)p^{6} (n -1)d^{x} ns^{2} . If n=4  the number of proton in the nucleus is

In an electrical circuit three incandescent bulbs A, B and C of rating 40 W, 60 W and 100 W respectively are connected in parallel to an electric source. Which of the following is likely to happen regarding their brightness? a. Brightness of all the bulbs will be the same b. Brightness of bulb A will be the maximum c. Brightness of bulb B will be more than that of A d. Brightness of bulb C will be less than that of B