Q1: Define Moment. Write its unit and formula.
Ans: Moment is the turning effect of a force about a point or axis.
Unit: Newton-meter (N·m)
Formula:
Moment = Force × Distance
M = F × d
Q2: State the types of Moment.
Ans: The types of moments are:
- ➔ Clockwise Moment
- ➔ Anticlockwise Moment
Q3: Define Line of Action.
Ans: Line of action is the imaginary straight line along which a force acts.
Q4: Define Torque. Write its formula.
Ans: Torque is the turning effect of a force about an axis.
Formula:
τ = F × r
Q5: What is Clockwise Torque?
Ans: Clockwise torque is the turning effect of a force that rotates a body in the clockwise direction.
Q6: What is Anticlockwise Torque?
Ans: Anticlockwise torque is the turning effect of a force that rotates a body in the opposite (anticlockwise) direction.
Q7: Define Couple of Forces.
Ans: A couple of forces consists of two equal and opposite forces acting parallel to each other but in opposite directions, producing rotation only.
Q8: State the principle of Moments.
Ans: The principle of moments states that for a body in equilibrium:
Sum of clockwise moments = Sum of anticlockwise moments
Q9: What is a Lever? What is it used for?
Ans: A lever is a rigid bar that rotates about a fixed point called fulcrum.
It is used to lift heavy loads with less effort.
Q10: State the principle of Lever.
Ans: The principle of lever states:
Effort × Effort arm = Load × Load arm
Q11: Name the types of Lever.
Ans: Types of levers are:
- ➔ Class I Lever
- ➔ Class II Lever
- ➔ Class III Lever
Q12: What is Class I Lever?
Ans: In Class I lever, the fulcrum lies between effort and load.
Example: Seesaw
Q13: What is Class II Lever?
Ans: In Class II lever, the load lies between fulcrum and effort.
Example: Wheelbarrow
Q14: What is Class III Lever?
Ans: In Class III lever, the effort lies between fulcrum and load.
Example: Human arm
Q15: State the mechanical advantage of Lever.
Ans: Mechanical Advantage (M.A) of a lever is:
M.A = Load / Effort
Also,
M.A = Effort arm / Load arm
Q16: What is Cranked Lever?
Ans: A cranked lever is a bent lever used to change the direction of force and provide better mechanical advantage.
Q17: State the uses of Cranked Lever.
Ans: Uses of cranked lever are:
- ➔ In machines to change direction of motion
- ➔ In engines
- ➔ In mechanical presses
Q18: What is Steel Yard?
Ans: A steel yard is a weighing device that uses the principle of moments to measure weight using a movable counterweight.
Q19: What is a Lever Safety Valve?
Ans: A lever safety valve is a device used in boilers to release excess pressure using a lever and weight system.
Q20: Describe the working principle of Safety Valve.
Ans: A safety valve works on the principle of moments.
When pressure inside the boiler increases beyond limit, it lifts the valve against the weight and releases steam, preventing explosion.
Q21: The mechanical advantage of a lever is 5. If its effort arm is 3m, find Load arm.
Ans: Given:
M.A = 5
Effort arm = 3 m
Formula:
M.A = Effort arm / Load arm
5 = 3 / Load arm
Load arm = 3 / 5 = 0.6 m
Final Answer:
Load arm = 0.6 m
