Kinematics (NEET (National Eligibility cum Medical Entrance Test) Physics): Questions 71  74 of 233
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Question number: 71
» Kinematics » Average Speed and Instantaneous Velocity
Question
The length of second’s hand in watch is 1 cm. The change in velocity of its tip in 15 seconds is
Choices
Choice (4)  Response  

a.  zero 

b.  cm/sec 

c.  cm/sec 

d.  cm/sec 

Question number: 72
» Kinematics » Average Speed and Instantaneous Velocity
Question
A person aiming to reach the exactly opposite point on the bank of a stream is swimming with a speed of 0.5 m/s at an angle of 120° with the direction of flow of water. The speed of water in the stream is
Choices
Choice (4)  Response  

a.  lm/s 

b.  0.433 m/s 

c.  0.25 m/s 

d.  0.5 m/s 

Question number: 73
» Kinematics » Motion in a Straight Line
Question
A man can swim with velocity v relative to water. He has to cross a river of width d flowing with a velocity u (w > v). The distance through which he is carried downstream by the river is x. Which of the following statements is correct?
Choices
Choice (4)  Response  

a.  If he crosses the river in minimum time x = du/v 

b.  x cannot be less than du/v 

c.  Force to be minimum he has to swim in a direction making an angle of π/2 sin 1 (v/u) with the direction of the flow of water. 

d.  x will be maximum if he swims in a direction making an angle of π/2 + sin1  1 (v/u) with direction of the flow of water. 

Question number: 74
» Kinematics » Scalars and Vectors » Scalar and Vector Products
Assertion (Ꭺ)
IfA + B= AB , then angle between A and B is 90°
Reason (Ꭱ)
A + B = B + A
Choices
Choice (4)  Response  

a.  Both Ꭺ and Ꭱ are false 

b.  Ꭺ is false but Ꭱ is true 

c.  Both Ꭺ and Ꭱ are true but Ꭱ is NOT the correct explanation of Ꭺ 

d.  Both Ꭺ and Ꭱ are true and Ꭱ is the correct explanation of Ꭺ 
