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science-physics

class VI

#### Key Concepts

pressure, force, gravitational force, frictional force, contact and non contact forces

#### essential questions

1. What is force?
2. How does force affect the motion of a body?
3. What are the various kinds of forces that are acting on a body?

#### Remembering:

1. Force is a: a) push  b) pull  c) both a and b   d) none of these
2. 1 newton= __dynes   a) 103   b) 104   c) 105   d) 106
3. Which of the following is an example of contact force: a) magnetic force  b) gravitational force  c)  electric force  d) muscular force
4. Force per unit area is____ a) thrust  b) pressure   c) buoyancy  d) density
5. Force has: a) only direction  b) only magnitude  c) both a and c   d) none of the above
6. Pascal is equal to: a) N/m²   b) N/m × s    c) N/cm²  d) N.m²
7. Define Force and its unit.
8. What is gravitational force?
9. Why does moon not fall like an apple on the earth? Research and explain with a diagram.
10. Will a man weighing 65 KG on equator weigh the same at the poles. Give reasons.
11. What are the two principles on which a spring balance works?

#### understanding:

1. Pressure is directly proportional to: a) density  b) height   c) acceleration due to gravity   d) all of these
2. Electrostatic force is a : a) contact force  b) non-contact force   c) balanced force  d) unbalanced force
3. when a cricketer catches the ball by his hands the force coming in action is:  a) non contact force   b) gravitational force  c) frictional force  d) both b and c
4. A stone falling from the roof of a house is due to: a) gravitational force   b) magnetic force  c) frictional force  d) electrostatic force
5. When a body is stationery: a) there is no force acting on it  b) force acting on it not in contact with it  c) combination of forces acting on it balances each other  d) body is in the vacuum
6. What is the difference between contact force and non contact force?
7. What is static friction. How is it different from Kinetic or Dynamic friction?
8. What is the relationship between dynamic and static friction. Explain using examples from real world.
9. How is rolling friction different from sliding friction?
10. Why is friction a necessary evil? Give 2 examples.
11. What is normal reaction force.

#### Application:

1. Two stones A and B of masses 2kg and 5kg respectively are released from same height in vacuum. which will reach on the ground first? a) stone A   b) stone B   c) both will reach at the same time   d) none of these
2. When a force of 10N is applied on a body it starts moving with a constant acceleration of 2m/s². the mass of the body is: a) 2kg  b) 0.2kg  c) 20kg  d) 5kg
3. How much pressure will be applied on a body. If a force of 4N is applied on its unit surface area.  a) 0.25 Pa   b) 2 Pa  c) 8Pa  d) 4Pa
4. A force of 12N is actin perpendicular on a wooden block. What will be the thrust on it: a) 12N  b) 24N  c) 48N  d)  6N
5. When a body is said to be under balanced forces then the resultant force applied on the body is: a) one   b) infinite  c) zero  d) none of these
6. Two bodies of masses m and 5m are moving under same magnitude of force. The ratios of their acceleration will be: a) 1: 5   b) 5:1  c) 1:25   d) 25:1
7. What force is needed to accelerate a 60Kg wagon from the rest to 5.0m/s² in  2.0 seconds: a) 100N   b) 120 N  c) 150N  d) 130N
8. Why do we feel warm when we rub our hands?
9. Rubbing two pebbles produce sparks. Can you explain how it happens?
10. What would happen if gymnast does not apply a little sand to their palms while holding rods? Give appropriate reasons for your answer.
11. Do you think body would have sunk inside the surface or fallen off the inclined plane if normal reaction force was missing. Give reasons for your answers.
12. Why are magnetic forces and electrostatic forces called non contact forces.
13. Why do camels and elephants have broad feet?
14. Why the foundations of high rise buildings are wide?
15. How do wide straps on school bags reduce pressure?
16. Why heavy trucks have 8 tires instead of 4.
17. The foot of an elephant area of 275 cm². If the mass of the elephant 2200Kg, find the pressure exerted by the elephant on the ground. (g=10m/s²)

#### Analysis:

1. Which point have more pressure in the container? a) point A   b) point B  c) point C  d) none of the above
2. Wooden block will  a) move in the direction of force A   b) move in the direction of force B   c) not move   d) none of these
3. the pressure of the water at the bottom of the pond is___ at the surface of the pond a) lower than   b) same  c) higher than  d) either lower or higher
4. Assertion A: The acceleration produced by a force in the motion of a body depends only up on its mass.  Reason R: Larger is the mass of the body, lesser will be the acceleration produced  a) Both A and R are true and R is the correct explanation of A  b) both A and R are true and but R is not the correct explanation of A  c) A is true but R is false   d) A is false but R is true
5. Assertion A: If the net external force on the body is zero, then its acceleration is zero  Reason R: Acceleration does not depend on force  a) Both A and R are true and R is the correct explanation of A  b) both A and R are true and but R is not the correct explanation of A  c) A is true but R is false   d) A is false but R is true
6. Assertion A:  An object can move with constant velocity if no net force acts on it.  Reason R: No net force is needed to move an object with constant velocity a) Both A and R are true and R is the correct explanation of A  b) both A and R are true and but R is not the correct explanation of A  c) A is true but R is false   d) A is false but R is true
7. Statement 1: It is easier to push a nail into a wooden box by pointed end  Statement2:  Nail’s head is easier to hit  Statement 3: Pressure applied on all nails is same whatever is their size a) Statement 1 and 3 are incorrect while statement 2 is correct  b) Statement 1 and 2 are incorrect while 3 is correct  c) All the statements are correct  d) all statements are incorrect
8. Statement1: Porters place a round piece of cloth on their heads. Statement 2:Pressure is inversely proportional to areas on which it acts  Statement 3: Pressure is independent of area of surface in contact a) Statement 1 and 3 are incorrect while statement 2 is correct  b) Statement 1 and 2 are incorrect while 3 is correct  c) All the statements are correct  d) all statements are incorrect