CONCEPTS OF BIOLOGY

  How Forces Affect Motion Class 9 Questions and Answers (Exercise) Revise, Reflect, Refine (NCERT Textbook Page No. 112) Question 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 with constant velocity, its acceleration is zero, so the net force must be zero. Therefore, the frictional force exerted by the floor is equal in magnitude and opposite to the applied force F.   Question 2. For a ball moving on a smooth, frictionless surface, choose the appropriate option that will make the following statements physically correct. (i) If no net force is applied on the ball, the velocity of the ball will remain the same/increase/decrease. (ii) If a net force is applied on the ball in the direction of its motion, the magnitude of the velocity of the ball will remain the same increase/decrease. (iii) If a net force is applied on the...

Class:- 8th Chapter:- 5. Exploring Forces Q.1: Match items in Column A with the items in Column B.   Column A (Type of force)   Column B (Example) (i) Muscular force (a) A cricket ball stopping on its own just before touching the boundary line (ii) Magnetic force (b) A child lifting a school bag (iii) Frictional force (c) A fruit falling from a tree (iv) Gravitational force (d) Balloon rubbed on woollen cloth attracting hair strands (v) Electrostatic force (e) A compass needle pointing North Solution: Column A (Type of force) Column B (Example) (i) Muscular force (b) A child lifting a school bag (ii) Magnetic force (e) A compass needle pointing North (iii) Frictional force (a) A cricket ball stopping on its own just before touching the boundary line (iv) Gravitational force (c) A fruit falling from a tree (v) Electrostatic force (d) Balloon rubbed on woollen cloth attracting hair strands Q.2. State whether the following statements are True or False. (i) : A force is always...

. Class 9 Science Exploration Chapter 5 Question Answer Class 9 Science Ch 5 Exploring Mixtures and Their Separation Question Answer Exploring Mixtures and Their Separation Class 9 Questions and Answers (Exercise) Revise, Reflect, Refine (NCERT Textbook Page No. 90) Question 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: (iv) Muddy water has large visible particles that settle quickly, making it heterogeneous. Milk shows Tyndall effect (light scattering) with suspended particles, appearing non-uniform. Blood contains cells that separate by centrifugation, behaving as heterogeneous. Brass is a uniform metal alloy throughout, makin...

  Science Class 8 Chapter 5 Question Answer Exploring Forces Exploring Forces Class 8 Question Answer (InText) Question 1. Why does it feel harder to pedal a bicycle when going uphill than on flat ground? (Page 62) Answer: When we cycle uphill, we’re constantly fighting against the Earth’s gravitational pull, which tries to pull us back down. This force acts perpendicular to the ground on a flat surface, meaning it doesn’t directly oppose our forward movement. But on a slope, a portion of the gravity acts against our direction of motion, requiring us to exert more force to move forward and upward. Question 2. Why is it easier to slip on a wet surface? (Page 62) Answer: It is easier to slip on a wet surface due to reduced friction between the foot and the surface. Water acts as a lubricant, minimizing the grip and making it easier to slide.   Question 3. Why do we feel ‘light’ or like we are ‘floating’ just after our swing reaches its highest point and begi...