This page covers Agniveer Navy MR Simple Machines with complete concept notes, 12 graded practice MCQs, key points and exam-specific tips. Free to study.
Core ConceptRead this first — the foundation of the topic
There are six basic simple machines
lever, pulley, inclined plane, wedge, screw, and wheel-and-axle. Each works on the principle of mechanical advantage, which means the output force is greater than the input force
KEY RULES
Mechanical Advantage (MA) = Output Force / Input Force
2
Work is always conserved
Input Work = Output Work (ignoring friction)
3. If MA > 1, the machine multiplies force. If MA < 1, it increases distance/speed.
4. Efficiency = (Useful Output Work / Input Work) × 100%
Formula BlockMemorise — at least one formula appears in every paper
Mechanical Advantage = Load / Effort
Work = Force × Distance
Efficiency (%) = (Output Work / Input Work) × 100
Velocity Ratio = Distance moved by effort / Distance moved by load
Exam PatternsWhat examiners ask — read before attempting PYQs
RRB Group D typically asks
(1) Calculate MA from given load and effort. (2) Identify which simple machine is shown in a diagram. (3) Compare efficiency or work done. (4) Real-world applications (e.g., ramps, scissors, door handles)
SHORTCUT
Always remember: No machine can have efficiency > 100% due to friction. If a question shows MA = 4 and efficiency = 80%, then useful work output is only 80% of what the ideal machine would give.
Worked ExampleSolve this step-by-step before moving on
A man uses a lever to lift a 600 N load. He applies an effort of 150 N. Find: (a) Mechanical Advantage, (b) Velocity Ratio if effort moves 2 m and load moves 0.4 m, (c) Efficiency.
Solution:
(a) MA = Load / Effort = 600 / 150 = 4
(b) Velocity Ratio = 2 / 0.4 = 5
(c) Efficiency = (MA / VR) × 100 = (4 / 5) × 100 = 80%
Exam TrapsCommon mistakes students make — avoid these
Students confuse Mechanical Advantage with Velocity Ratio. MA compares forces; VR compares distances. They're different values!
Also, assuming a machine with high MA has high efficiency—not always true due to friction losses.
Key Points to Remember
Simple machine multiplies force (effort) by reducing distance moved or changing force direction.
Mechanical Advantage = Load / Effort; value >1 means force is multiplied.
Velocity Ratio = Distance moved by effort / Distance moved by load; always independent of friction.
Efficiency = (Useful Work Output / Work Input) × 100%; always <100% in real machines.
Six types: lever, pulley, inclined plane, wedge, screw, wheel-and-axle.
Remember: Work input = Work output (ideal); efficiency accounts for friction losses.
Exam-Specific Tips
Mechanical Advantage formula: MA = Load / Effort (dimensionless ratio).
Velocity Ratio formula: VR = Distance moved by effort / Distance moved by load (always > MA in real machines).
Efficiency formula: η = (MA / VR) × 100%; always expressed as percentage.
Class 1 Lever has fulcrum between effort and load; MA can be >1, =1, or <1 depending on position.
Class 2 Lever has load between fulcrum and effort; always MA >1 (mechanical advantage guaranteed).
Class 3 Lever has effort between fulcrum and load; always MA <1 (speed and range advantage).
Ideal Machine (frictionless): MA = VR; Real Machine: MA < VR always due to friction.
Inclined Plane MA = Length of slope / Height of slope; reduces effort needed to lift vertically.
Practice MCQs
Simple Machines — Practice Questions
12graded MCQs · easy to hard · full solution & trap analysis
A lever of length 2 m has its fulcrum at 0.5 m from the load end. If a force of 100 N is applied at the free end, what is the mechanical advantage of this lever?
Practice 2easy
In a pulley system, if a movable pulley is used to lift a load of 200 N, what minimum effort force is required (neglecting friction and pulley weight)?
Practice 3easy
A wedge is used to split wood. Which statement correctly describes the relationship between the angle of the wedge and its mechanical advantage?
Practice 4easy
A screw with a pitch of 2 mm is rotated 10 complete turns to fasten it into wood. What is the linear displacement of the screw?
Practice 5medium
A lever of length 2 m has its fulcrum at 0.5 m from the load end. If a load of 100 N is placed at the load end, what effort is needed to balance it (assuming a massless lever)?
Practice 6medium
Which type of simple machine is represented by a staircase?
Practice 7medium
A movable pulley system has a mechanical advantage of 4. If the load is 400 N, what is the minimum effort required to lift it (ignoring friction)?
Practice 8medium
A wedge is used to split wood. Which principle of simple machines does it apply?
Practice 9medium
In a screw, the mechanical advantage depends on which of the following?
Practice 10hard
A lever of class 1 has a load of 100 N at a distance of 2 m from the fulcrum. If the effort is applied at a distance of 5 m from the fulcrum, what is the mechanical advantage of this lever?
Practice 11hard
A movable pulley system is used to lift a load of 600 N. If the efficiency of the system is 75% and the mechanical advantage is 4, what is the effort force required?
Practice 12hard
An inclined plane has a length of 10 m and a height of 2 m. What is the ideal mechanical advantage of this inclined plane, assuming it is frictionless?
60-Second Revision — Simple Machines
Formula: MA = Load / Effort; VR = Distance by effort / Distance by load; Efficiency = (MA/VR) × 100.
Remember: No real machine has efficiency = 100%; friction always reduces useful output work.
Trap: High MA doesn't mean high efficiency—check friction losses and compare MA to VR.
Class 1 Lever (fulcrum centre) varies MA; Class 2 (load centre) MA always >1; Class 3 (effort centre) MA always <1.
Quick Check: If MA = 5 and VR = 6, efficiency = (5/6)×100 ≈ 83%—this is realistic and acceptable.