List any three human activities that you | Class 9 Science Chapter Natural Resources, Natural Resources NCERT Solutions

Abdul, while driving to school, computes the average speed for his trip to be 20 km h^-1. On his return trip along the same route, there is less traffic and the average speed is 40 km h^-1. What is the average speed for Abdul’s trip?

An object of mass 40 kg is raised to a height of 5 m above the ground. What is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half-way down.

A driver of a car travelling at 52 km h^-1 applies the brakes and accelerates uniformly in the opposite direction. The car stops in 5 s. Another driver going at 3 km h^-1 in another car applies his brakes slowly and stops in 10 s. On the same graph paper, plot the speed versus time graphs for the two cars. Which of the two cars travelled farther after the brakes were applied?

Fig 8.11 shows the distance-time graph of three objects A,B and C. Study the graph and answer the following questions:

          Fig. 8.11

(a) Which of the three is travelling the fastest?
(b) Are all three ever at the same point on the road?
(c) How far has C travelled when B passes A?
(d) How far has B travelled by the time it passes C?

Two objects, each of mass 1.5 kg, are moving in the same straight line but in opposite directions. The velocity of each object is 2.5 m s^-1 before the collision during which they stick together. What will be the velocity of the combined object after collision?

Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her? Why?

Two objects of masses 100 g and 200 g are moving along the same line and direction with velocities of 2 m s^-1 and 1 m s^-1, respectively. They collide and after the collision, the first object moves at a velocity of 1.67 m s^-1. Determine the velocity of the second object.

How do poriferan animals differ from coelenterate animals?

The speed-time graph for a car is shown is Fig. 8.12.

          Fig. 8.12

(a) Find how far does the car travel in the first 4 seconds. Shade the area on the graph that represents the distance travelled by the car during the period.
(b) Which part of the graph represents uniform motion of the car?

How are sol, solution and suspension different from each other?

Draw well labelled diagrams of various types of muscles found in human body.

A sonar device on a submarine sends out a signal and receives an echo 5 s later. Calculate the speed of sound in water if the distance of the object from the submarine is 3625 m.

Which one of the following is a correct electronic configuration of sodium?
(a) 2,8        (b) 8,2,1        (c) 2,1,8        (d) 2,8,1.

If you are provided with some vegetables to cook. You generally add salt into the vegetables during cooking process. After adding salt, vegetables release water. What mechanism is responsible for this?

If Z = 3, what would be the valency of the element? Also, name the element.

If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen?

What are polyatomic ions? Give examples.

What are the characteristics of the particles of matter?

Fill in the blanks
(a) Five kingdom classification of living organisms is given by ———.
(b) Basic smallest unit of classification is ———.
(c) Prokaryotes are grouped in Kingdom ———.
(d) Paramecium is a protista because of its ———.
(e) Fungi do not contain ———.
(f) A fungus ——— can be seen without microscope.
(g) Common fungi used in preparing the bread is ———.
(h) Algae and fungi form symbiotic association called ———.

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 solid state directly to vapour 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———.