UNIT-1: Chapter-2
FORCES AND SHAPE
সুপ্রিয় ২০২৪ সালের ‘O’ level পরীক্ষার শিক্ষার্থী বন্ধুরা, শুভেচ্ছা নিও। আজ তোমাদের Physics Paper-1 -এর ‘UNIT-1: Chapter-2, FORCES AND SHAPE’ থেকে বাকি Discussion নিয়ে আলোচনা করা হলো।
Force against extension graph
Figure- Rubber bands do not obey Hooke’s law- the extension is not directly proportional to the force causing it.
Hooke’s Law: Essentials
Specification Point 1.23
* Know that the initial linear region of a force-extension graph is associated with Hooke’s law
* Hooke’s law states that:
* The extension of a spring is proportional to the applied force.
* Many other materials (such as metal wires) also obey Hooke’s law.
* Hooke’s law is associated with the initial linear (straight) part of a force-extension graph.
The initial linear part of a force-extension graph is consistent with Hooke’s law
The Elastic Limit
Specification Point 1.24
* Describe elastic behavior as the ability of a material to recover its original shape after the forces causing deformation have been removed
* Objects that obey Hooke’s law will return to their original length after being stretched.
* If an object continues to be stretched it can be taken past its elastic limit. At this point the object will no longer obey Hooke’s law and will not return to its original length.
The spring on the right has exceeded its elastic limit
Exam Tip
* A relationship is said to be proportional if the graph is a straight line going through the origin.
* If a graph is a straight line but does not go through the origin the relationship is said to be linear.
WORK EXAMPLE 3.1
Represent on an arrow diagram, a velocity of 20 ms-1 in the direction of N45⁰E.
Solution: Step 1: Choose an appropriate scale. In this case, we may choose 1 cm to represent 5 ms-1.
Step 2: The length of the arrow will represent the magnitude of the vector. To represent a velocity of 20 ms-1 using the above scale, the length of the arrow would be 4 cm.
Step 3: Using a protractor, measure an angle N45⁰E. The arrow diagram is shown in Figure 3.8.
Scale: 1cm: 5 ms-1
WORK EXAMPLE 3.1
Figure 3.15 below shows two horizontal forces of magnitude 15 N and 20 N, acting in perpendicular directions on a mass, M. Determine the resultant force acting on the mass.
Assistant Teacher (Senior section)
O and A level Physics Teacher
Bangladesh International School and College, Dhaka.
কলি
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