9th Physics Chapter 2 Constructed response questions
9th Physics Chapter 2 Constructed response questions. We will solve only 9th class physics revised syllabus.
2.1 Distance and displacement may or may not be equal in magnitude. Explain this statement.
Distance is the total path covered by an object but displacement is the shortest distance. If the total path covered by an object is the shortest distance the distance will be displacement. Distance and displacement will be equal only if the object is moving in a straight path without changing direction.
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2.2 When a bullet is fired, its velocity with which it leaves the barrel is called the muzzle velocity of the gun. The muzzle velocity of one gun with a longer barrel is lesser than that of another gun with a shorter barrel. In which gun is the acceleration of the bullet larger? Explain your answer.
$$v_f^2-v_i^2=2as\\Bullet\;starts\;from\;rest\\So,\;initial\;velocity\;will\;be\;0\\v_f^2-0=2as\\v_f^2=2as\\\frac{v_f^2}{2s}=a\\a=\frac{v_f^2}{2s}$$
The above relation shows that acceleration is inversely proportional to the distance. So, the shorter barrel gun will have the larger acceleration.
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2.3 For a complete trip, average velocity was calculated. Its value came out to be positive. Is it possible that its instantaneous velocity at any time during the trip had the negative value? Give justification of your answer.
Yes it is possible because an object can move backward at some instants during the trip. At that instant its instantaneous velocity will be negative. However, average velocity can be calculated by dividing the total distance with total time. Average velocity depends only on starting and ending points.
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2.4 A ball is thrown vertically upward with velocity v. It returns to the ground in time t. Which of the following graphs correctly represents the motion? Explain your reasoning.
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2.5 The figure given below shows the distance – time graph for the travel of a cyclist. Find the velocities for the segments a, b and c.
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2.6 Is it possible that the velocity of an object is zero at an instant of time, but its acceleration is not zero? If yes, give an example of such a case.
Yes it is possible. When we throw a ball vertically upward its velocity will be zero at the highest point but its acceleration will not be zero at that instant. At that point its acceleration will be acceleration due to gravity i.e 9.8 meter per second square.
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