Class 9th Physics Unit 4 Turning Effect of Forces

physics 9th notes Chapter No 4

1. The rotation produced in a body depends upon —- factors:

 
 
 
 

2. A meter rod on a wedge is an example of_____ equilibrium

 
 
 
 

3. When an object is resting on the smooth horizontal surface, the weight of the object is balanced by :  

 
 
 
 

4. If the direction of parallel forces is the opposite, then these are called forces:

 
 
 
 

5. The _____ of a racing car is kept low to make its stable:

 
 
 
 

6. The rotational effect of a body is measured by a quantity known as:

 
 
 
 

7. A______is always acting while openingor closing water tap, a lock, stopper of a bottle or jar:

 
 
 
 

8. The centre of gravity of cylinder is the:

 
 
 
 

9. The equilibrium in which the body does not come back to its original condition when set free after slightly lifting from one side isequilibrium:

 
 
 
 

10. In Stable equilibrium, the centre of gravity than the original position is

 
 
 
 

11. There are how many conditions of equilibrium?

 
 
 
 

12. The direction of Torque is determined by —– rule:

 
 
 
 

13. A book lying on the table is an example of——equilibrium:

 
 
 
 

14. If the rotation is produced in clock wise direction then the Torque is taken as:

 
 
 
 

15. The Torque produced in a body due to a couple is equal to the product of one of the forces and the

 
 
 
 

16. Torque is a quantity:

 
 
 
 

17. The centre of gravity of triangle is the:

 
 
 
 

18. A force of 10 N is making an angle of 30ᵒ with the horizontal. Its horizontal component will be:

 
 
 
 

19. In Unstable equilibrium, the centre of gravity is _____ than the original position:

 
 
 
 

20. The equilibrium in which the body comes back to its original condition when set free after slightly lifting from one side is

 
 
 
 

21. There are how many states of equilibrium?

 
 
 
 

22. In System International, the unit of Torque is:

 
 
 
 

23. The centre of gravity of a regular shaped body is always on its centre of

 
 
 
 

24. If a number of forces act on a body such that their points of action are different but lines of action are parallel to each other than these forces are known asforces:

 
 
 
 

25. The Torque in ceiling fan rotating at constant speed is:

 
 
 
 

26. Component of a vector acting along the x – axis is called:

 
 
 
 

27. When the sum of all the force acting on a body is zero or the object is moving with uniform velocity then it will be in

 
 
 
 

28. When two equal, opposite and parallel forces act at two points of the same body, they form a:

 
 
 
 

29. The centre of gravity of parallelogram, rectangle, square is the:

 
 
 
 

30. First condition of equilibrium is represented by:

 
 
 
 

31. Value of sin 30ᵒ:

 
 
 
 

32. Addition of vectors are done by:

 
 
 
 

33. According to First condition of equilibrium, the sum of all the forces acting on the body should be

 
 
 
 

34. Sigma is the Greek letter which is used to represent:

 
 
 
 

35. In Neutral equilibrium, the centre of gravity _____ than the original position:

 
 
 
 

36. If the direction of parallel forces is the same, then these are called forces:

 
 
 
 

37. The position of the centre of gravity depends upon

 
 
 
 

38. If the rotation produced in anticlock wise direction then the Torque is taken as:

 
 
 
 

39. Motion of the football on the ground is an example of______equilibrium:

 
 
 
 

40. Second condition of equilibrium is represented by:

 
 
 
 

41. Component of a vector acting along the y – axis is called:

 
 
 
 

42. The point at which whole weight of the body appears to act is called:

 
 
 
 

43. The force which is acting perpendicularly downwards towards the earth is called:

 
 
 
 

44. According to Second condition of equilibrium, the sum of all the Torques acting on the body should be

 
 
 
 

45. If the centre of gravity of the body is below the fulcrum then the body will be in equilibrium:

 
 
 
 

Short Questions

Can a small child play with a fat child on the seesaw? Explain how?
Can the nut of the axle of a bike be loosened with hand why we use a spanner for this purpose?
Define a couple. Describe its role in steering wheel double arm spanner?
Define Axis of Rotation.
Define centre of gravity.
Define equilibrium.
Define like and unlike parallel force?
Define Moment arm.
Define Resolution of Forces.
Define Resultant Force
Define Resultant Vector
Define Rigid Body?
Define terminal velocity?
Define the moment arm.
Define the resultant vector?
Define Torque
Define Torque. What is its unit? On what factors Torque (moment of a force) depends?
Define Torque. Write its formula and unit?
Define Trigonometric Ratios. Give Examples
Define types of moment.
Describe the principle of the moment?
Differentiate between axis of rotation and point of rotation?
Differentiate between Stable and neutral equilibrium
Differentiate between Torque and couple
Discuss the stability and position of center of mass with the reference of example?
Does the fan satisfy second condition for equilibrium when rotating with uniform speed?
Does the speed of a ceiling fan go on increasing all the time?
Explain how center of mass helps the system to move as well as rotate?
Explain the first condition for equilibrium.
Give a few examples in which lowering of center of mass make the objects stable?
Give an example of a moving body, which is in equilibrium.
How can a force be resolved into its rectangular components?
How can we increase Torque by keeping the force constant?
How does a paratrooper come down?
How head to tail rule helps to find resultant of forces?
List the center of gravity of some symmetrical objects?
Name some more objects that work by the turning effects of forces.
Name some objects that work by the turning effects of forces.
Sketch values of Trigonometric values at different angles.
State Second Condition for Equilibrium.
State the conditions of equilibrium.
Think of a body that is in rest but not in equilibrium.
Two children are sitting on the see-saw, such that they cannot swing. What is the net Torque in this situation?
What do you mean by a line of action of a force?
What do you mean by a rigid body?
What do you mean by newton-meter (Nm)?
What do you mean by the axis of rotation?
What is equilibrium?
What is meant by parallel forces?
What is meant by principle of moments?
What is meant by trigonometry? Give some important trigonometric ratios.
What is the second condition for equilibrium?
When a body is said to be in equilibrium?
Why a body cannot be in equilibrium due to a single force acting on it?
Why a vehicle is made heavy at its bottom?
Why do we prefer a spanner of longer arm for loosening or tightening a nut?
Why do we put handle of the door at its extreme edge?
Why it is easy to open and close the door by pulling or pushing it as it handles?
Why it is easy to tighten a nut using a spanner of the longer arm than a spanner of the shorter arm?
Why the handle of a door is fixed near the outer edge of a door?
Why the height of the vehicles is kept as low as possible?
Why there is a need for second condition of equilibrium if a body satisfies first condition of equilibrium?
With a little effort, we can learn to balance a stick vertically up on our fingertip how this is possible?
Women and children in the villages often carry pitchers with water on their heads how this is possible?
Write factors effecting Torque

Long Questions

 

A block of mass 10 kg is suspended at a distance of 20 cm from the center of a uniform bar 1 m long. What force is required to balance it at its center of gravity by applying the force at the other end of the bar?  
A force is acting on a body making an angle of 30⁰ with the horizontal. The horizontal component of the force is 20 N. Find the force.
A force of 100 N is applied perpendicularly on a spanner at a distance of 10 cm from a nut. Find the Torque produced by the force.
A force of 150 N can loosen a nut when applied at the end of spanner 10 cm long. What should be the length of the spanner to loosen the same nut with a 60 N force? How much force would be sufficient to loosen it with a 6 cm long spanner?
A nut has been tightened by a force of 200 N using 10 cm long spanner. What length of a spanner is required to loosen the same nut with 150 N force?
A picture frame is hanging by two vertical strings. The tensions in the strings are 3.8 N and 4.4 N. Find the weight of the picture frame. 
Briefly explain the states of equilibrium?
Define and explain the three states of equilibrium.
Define Couple. Give examples and find Torque produced by couple.
Describe the conditions of Equilibrium
Explain an experiment to find the center of gravity of a four-sided plate of uniform thickness. How can you verify your answer by using geometry?
Explain an experiment to find the center of gravity of an irregular shaped thin lamina?
Explain the first condition of equilibrium.
Explain the resolution of the vector?
Explain Torque or moment of a force.
Explain what is meant by stable, unstable and neutral equilibrium. Give one example in each case.
Find the magnitude and direction of a force, if its x-component is 12 N and y-component is 5 N.
Find the magnitude and direction of a vector whose rectangular components are given.
Find the perpendicular components of a force of 50 N making an angle of 30⁰ with x-axis.
Find the resultant of the following forces: (a) 10 N along x-axis (b) 6 N along y-axis (c) 4 N along negative x-axis.
How a force be resolved into its rectangular components?
How Stability and Position of centre of mass are related to each other?
Resolve the vector into its rectangular components.
The steering of a car has a radius 16 cm. Find the Torque produced by a couple of 50 N.
What is Centre of Mass? Explain its effect on rotation.
What is equilibrium? State and explain the conditions of equilibrium.
What is meant by centre of gravity of a body? Explain an experiment to find the centre of gravity of a plate of uniform thickness.
Which method is used for addition of forces? Explain with example.

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