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PHYSICS [2 Mark Question Answer]

Simple Machines · ICSE STD 6 (ICSE - English Medium). 23 questions.

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[2 Mark Question Answer]

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23 questions · timed · auto-graded

Question 12 Marks
Define the term efficiency of a machine.
Answer
The ratio of the work done by the machine to the work done on the machine is called the efficiency of a machine
$
\text { Efficiency }=\frac{\text { Output energy }}{\text { Input energy }}
$
(Work done by a machine is called the output energy and the work done on a machine is called the input energy.)
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Question 22 Marks
Explain the term mechanical advantage of a machine.
Answer
The mechanical advantage of a machine is the ratio of the load to time effort. In other words. Mechanical advantage (M.A.) $=\frac{\operatorname{Load}( L )}{\operatorname{Effort}( E )}$
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Question 32 Marks
Define the term ‘work input’ and ‘work output’ in relation to a machine.
Answer
Work input is work done on a machine equal to the effort force times the distance through which the force is applied.
Work output is work that is done by a machine equals resistance force times the distance through which the force applied.
For an ideal machine, the work output is equal to the work input i. e. the efficiency.
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Question 42 Marks
What are the wheel and axle? Give two examples.
Answer
The wheel and axle is a simple machine having a wheel and an axle. The linear motion of the axle is obtained by rotating the wheel so as to reduce friction.
Example: Steering wheel, screwdrivers, water tap, etc.
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Question 52 Marks
What is a screw? Give two examples.
Answer
A screw is a simple machine that appears like an inclined plane wound around a rod with a pointed tip.
Examples:ajar lid, a drill.
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Question 62 Marks
Draw diagram to illustrate the position of fulcrum, load, and effort, of the following:
a pair of forceps
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Question 102 Marks
What is an ideal machine?
Answer
A machine in which no part of the work done on the machine is wasted is called an ideal or perfect machine. Thus, for an ideal machine, the work output is equal to the work input, i.e., the efficiency of an ideal machine is 1 (or 100 percent).
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Question 112 Marks
The mechanical advantage of a machine is 2. It is used to raise a load of 15 kgf. What effort is needed?
Answer
Given,
Mechanical advantage $=2$
Load $=15 Kgf$
Mechanical advantage $=\frac{\text { Load }}{\text { Effort }}$
Effort $=\frac{\text { Load }}{\text { Mechanical advantage }}$
$=\frac{15}{2}$
$=7.5 kgf$
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Question 122 Marks
The mechanical advantage of a machine is 5. How much load it can exert for the effort of 2 kgf?
Answer
Given,
Mechanical advantage $=5$
Effort $2 kgf$
Mechanical advantage $=\frac{\text { Load }}{\text { Effort }}$
$\Rightarrow$ Load $=$ Mechanical advantage $\times$ Effort
$=5 \times 2 kgf =10 kgf$
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Question 132 Marks
In a machine, an effort of 10 kgf is applied to lift a load of 100 kgf. What is its mechanical advantage?
Answer
Given,
$
\begin{aligned}
& \text { Load }=100 kgf \\
& \begin{aligned}
& \text { Effort }=10 kgf \\
& \text { Mechanical advantage }=\frac{\text { Load }}{\text { Effort }} \\
&=\frac{100 kgf }{10 kgf }=10
\end{aligned}
\end{aligned}
$
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Question 142 Marks
Solve the following numerical problem.
What effort will be required to lift a load of 500 N by a single movable pulley? [Hint: Mechanical advantage of a single movable pulley is two].
Answer
Load $=500 N$
Mechanical advantage (M A) $=2$
of a single movable pulley
Effort $=$ ?
We know that,
$
\text { MA }=\frac{\text { Load }}{\text { Effort }}
$
$\Rightarrow$ Effort $=\frac{500}{2} N=250 N$
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Question 152 Marks
Solve the following numerical problem.
Calculate the mechanical advantage of a crowbar of length 240 cm if its fulcrum is situated at a distance of 40 cm from the load.
Answer
Length of crowbar $=240 cm$
Length of load arm $=40 cm$
Length of effort $arm =240 cm -40 cm$
$
=200 cm
$
Mechanical advantage $=\frac{\text { Load }}{\text { Effor }}=\frac{\text { Effort arm }}{\text { load arm }}$
$
=\frac{200 cm }{40 cm }=5
$
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Question 162 Marks
Solve the following numerical problem.
The length of the load arm of a lever is 6 m long and the effort arm is 3 m long. What is the effort required to lift a load of 40 N?
Answer
Length of the load arm $=6 m$
Length of the effort arm $=3 m$
Load $=40 N$
Effort $=$ ?
We know that
$
\frac{\text { Load }}{\text { Effort }}=\frac{\text { Effort arm }}{\text { Load arm }}
$
By putting values, we get
$
\begin{aligned}
& \frac{40 N }{\text { Effort }}=\frac{3 m }{6 m } \\
\Rightarrow & \text { Effort }=\frac{40 \times 6}{3}=80 N
\end{aligned}
$
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Question 172 Marks
Solve the following numerical problem.
The length of a lever is 2 m. Calculate its mechanical advantage if the fulcrum is situated at a distance of 40 cm from the effort.
Answer
Length of the lever $2 m =200 cm$
Length of the effort $\operatorname{arm} 40 cm$
Length of the load arm $200 cm -40 cm =160 cm$
Mechanical advantage?
We know that,
Mechanical advantage $=$ Length of effort arm $/$ Length of load arm
$
M A=\frac{40 cm }{160 cm }=0.25
$
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Question 182 Marks
Answer the following in detail.
How does a pulley make work simpler?
Answer
A pulley is a wheel or a circular disc that can rotate freely about its axle. It is used to lift heavy objects. It is neither a force multiplier nor a speed multiplier. It only changes the direction of the applied force from upwards against gravity to downwards towards gravity. There are two types of pulley systems – Single fixed pulley and single movable pulley.
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Question 192 Marks
Answer the following in short.
What do you understand by the term efficiency of a machine’?
Answer
The ratio of the work done by the machine to the work done on the machine is called the efficiency of a machine
$
\text { Efficiency }=\frac{\text { Output energy }}{\text { Input energy }}
$
[Work done by a machine is called the output energy and the work done on a machine is called the input energy.]
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Question 202 Marks
Answer the following in short.
Using a suitable example, describe how a machine acts as a force multiplier.
Answer
It is very difficult to open the sealed metal cap of a cold drink bottle with our bare hands. A simple machine like a bottle opener (Class II lever) multiplies the applied force and much less effort is required to open the cap. Hence, it acts as a force multiplier.
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Question 212 Marks
Answer the following in short.
What is the function of a screw? Give anyone the use of a screw.
Answer
A screw is a special type of an inclined plane that has a sharp and pointed tip and can be turned (using a screwdriver, bolt, or a jack.) It acts as a force multiplier and less effort is required to do the work. Example: Screw forced and rotated into wood travels a greater distance with less effort than a nail would. Bolt rotating inside the fixed nut and jack used to lift a car using the principle of the screw.
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Question 222 Marks
Answer the following in a word or two or in a sentence.
Write the formula for calculating the efficiency of a machine.
Answer
$
\text { Efficiency }=\frac{\text { Output energy }}{\text { Input energy }}
$
The percentage value of efficiency of a machine is calculated as
$
\text { Efficiency }=\frac{\text { Output energy }}{\text { Input energy }} \times 100 \%
$
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Question 232 Marks
Answer the following.
State the principle of levers.
Answer
The principle of a lever states that the product of the load and the load arm is always equal to the product of the effort and the effort arm.
Load x Load arm = Effort x Effort arm Load Effort arm
$
\frac{\text { Load }}{\text { Effort }}=\frac{\text { Effort arm }}{\text { Load arm }}
$
The above ratio is called the mechanical advantage of a lever.
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[2 Mark Question Answer] - PHYSICS STD 6 Questions - Vidyadip