**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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