CBSE Class 9 Sample Papers, Syllabus, Test Papers & NCERT Solutions

Think It Over (Page No. 140) 1. Are atoms the smallest indivisible particles? Answer: No, atoms are not the smallest indivisible particles. Scientists discovered that atoms are made up of even smaller subatomic particles — electrons, protons, and neutrons. The discovery of electrons by J.J. Thomson (1897), protons by Rutherford, and neutrons by James Chadwick […]

Revise, Reflect, Refine 1. State whether True or False. (i) Work is said to be done when a force is applied, even if the object does not move. (ii) Lifting a bucket vertically upward results in positive work done on the bucket. (iii) The SI unit for both work and energy is joule (J). (iv) […]

Think It Over (Page No. 116) 1. What will be the magnitude of velocity of the child at the bottom of the blue slide? Answer: Using conservation of mechanical energy (ignoring friction), the potential energy at the top converts entirely to kinetic energy at the bottom: mgh=12mv2mgh = \frac{1}{2}mv^2 v=2ghv = \sqrt{2gh} So if the […]

Revise, Reflect, Refine 1. Using a horizontal force F, a table is moved across the floor at a constant velocity. How much is the frictional force exerted by the floor on the table? Answer: Since the table moves at constant velocity, acceleration = 0, so net force = 0. This means frictional force = applied […]

Think It Over (Page No. 94) 1. Why does a canoe move forward when the canoeist pushes water backwards with their paddle and why does it move faster when they push harder? Answer: By Newton’s 3rd Law, when the paddle pushes water backward, water pushes the paddle forward with equal and opposite force, moving the […]

Revise, Reflect, Refine 1. Which of the following mixtures are correctly classified as homogeneous (Hm) and heterogeneous (Ht)? Choose the correct option. (i) Air— Hm, Milk— Ht, Sugar solution— Hm, Smoke— Hm (ii) Brass— Ht, Fog— Ht, Vinegar— Ht, Muddy water— Hm (iii) Copper sulfate solution— Hm, Salt solution— Hm, Milk— Hm, Bronze— Hm (iv) Muddy water— Ht, Milk— Ht, Blood— Ht, Brass— Hm Answer: The correct answer is (iv) Muddy […]

Think It Over (Page No. 72) 1. Why do suspended particles settle in muddy water over time but not in milk? Answer: Muddy water is a suspension, where particles are large and heavy. Due to gravity, these particles settle down at the bottom when left undisturbed. Milk, on the other hand, is a colloid. Its […]

Revise, Reflect, Refine 1. My father went to a shop from home which is located at a distance of 250 m on a straight road. On reaching there, he discovered that he forgot to carry a cloth bag. He came home to take it, went to the shop again, bought provisions and came back home. […]

Think It Over (Page No. 48) 1. How much distance should we maintain from the truck ahead to avoid a collision if it suddenly applies the brakes? Answer: We should maintain a safe distance so that if the truck suddenly applies brakes, our vehicle has enough distance to stop and avoid collision. This stopping distance […]

Revise, Reflect, Refine 1. Meristematic tissues divide repeatedly. What property of their cells allows them to do this? (i) They have thick walls for protection. (ii) They contain large vacuoles that store nutrients. (iii) They have thin walls, dense cytoplasm and large prominent nucleus. (iv) They are functionally differentiated cells. Answer: Correct option: (iii) They […]