Answer key

Prepared by: learnloophq@gmail.com

Last edited 26 days ago by Learn LoopHQ.

Chapter: 05. Simple Machine

⁠

Simple Machines: Practice Exam - Answer Key

Section A: Multiple Choice Questions (MCQs)

b) They always have 100% efficiency.

a) First order lever

c) Fulcrum

c) Screw

b) Second order lever

Section B: Fill in the Blanks

faster

load

mechanical advantage

second order

inclined plane

wedge

wheel and axle

pulley

lubricated (or oiled)

compound machine

Section C: True/False Questions

FALSE

TRUE

FALSE

TRUE

Section D: Explanations of Terms

Simple Machines: Simple machines are devices with very few parts that change the direction or magnitude of force, making work easier and faster.

Effort Arm: The effort arm is the shortest distance from where the effort is applied on a machine to the fulcrum or pivot point.

Efficiency of a machine: Efficiency is the ratio of the useful output energy a machine produces to the total input energy supplied to it, indicating how well it converts energy into work.

Section E: Diagram-Based Questions

a) This diagram illustrates a lever. b) One real-life example of this specific class (first-order) of simple machine is a crowbar.

a) The simple machine being used in this picture is an inclined plane. b) This machine makes the work easier by allowing the heavy barrel to be moved over a longer, gentler slope instead of being lifted straight up, which requires less direct force.

Section F: Short Answer Questions

Three advantages of using machines in daily life are: they help to do work with less effort, they allow us to do work faster, and they enable us to do unsafe or dangerous work safely.

A single fixed pulley primarily changes the direction of the effort, allowing for a more convenient pull (e.g., pulling down to lift up). In contrast, a single movable pulley multiplies the force, allowing a load to be lifted with less effort, as the load is supported by two segments of the rope.

Compound machines tend to have lower efficiency than simple machines because they have multiple moving parts. This results in more friction within the system, leading to a greater loss of input energy, usually as heat and sound, rather than useful work.

Given: Rahul’s weight (Effort) = 35 kgf, Rahul’s distance (Effort arm) = 84 cm. Gaurav’s weight (Load) = 42 kgf, Gaurav’s distance (Load arm) = ?. Using the Law of Levers: Effort × Effort arm = Load × Load arm 35 kgf × 84 cm = 42 kgf × Load arm 2940 = 42 × Load arm Load arm = 2940 / 42 = 70 cm. Gaurav must sit 70 cm from the fulcrum to balance Rahul.

Section G: Differentiate Concepts

Load Arm is the shortest distance from the point where the load is acting to the fulcrum of a lever. Effort Arm is the shortest distance from the point where the effort is applied to the fulcrum of a lever.

Section H: Environmental Awareness / Everyday Use

Taking proper care of machines helps conserve the environment in two main ways:

It extends the lifespan of machines, reducing the frequency of replacement. This saves raw materials and energy that would be used in manufacturing new machines.

Well-maintained machines operate more efficiently, often consuming less energy (e.g., electricity or fuel), which reduces overall energy use and associated carbon emissions.

Section I: Long Answer Questions

Levers are classified based on the position of the fulcrum (F), load (L), and effort (E). A first-order lever has the fulcrum between the load and the effort (L-F-E), such as a crowbar. A second-order lever has the load between the fulcrum and the effort (F-L-E), for instance, a wheelbarrow. A third-order lever has the effort between the fulcrum and the load (F-E-L), like a fishing rod. Each type serves different purposes in terms of force multiplication, speed, or range of motion.

An ideal machine is a theoretical concept where the machine operates without any energy loss due to friction, meaning its output energy is equal to its input energy, resulting in 100% efficiency. This is not achievable in practice because friction is always present between moving parts, converting some input energy into unusable forms like heat or sound. The two main factors that determine a machine’s ability to do work are its mechanical advantage (how much it multiplies force) and its efficiency (how well it converts input energy into useful output).

Want to print your doc?
This is not the way.

Try clicking the ⋯ next to your doc name or using a keyboard shortcut (

CtrlP

) instead.