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Dynamics Quiz Please click on the hyperlink to start the quiz Next

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Question 1 The balloon of weight 500 N (mass 50 kg) moves downwards with a constant velocity of 2m/s. Assume the only other force acting on the object is the air resistance. What is the resultant force acting on the balloon? What is the resultant force acting on the balloon? A. 0 NA. 0 N B. 100 N B. 100 N A. 0 NB. 100 N C. 400 NC. 400 N D. 500 N D. 500 N C. 400 ND. 500 N

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Option A You are right!!! Since it is moving with constant velocity, the acceleration will be 0. Thus the resultant force is 0 N. Go to the question 2 question 2question 2

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Option B The acceleration is not 2m/s 2. The balloon is moving with constant velocity of 2 m/s. Hint : What is the acceleration of an object with constant velocity? Go back to Question 1 Question 1Question 1

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Option C The acceleration is not 2m/s 2. The balloon is moving with constant velocity of 2 m/s. Hint : What is the acceleration of an object with constant velocity? Go back to Question 1 Question 1Question 1

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Option D The question asks for the resultant force not the opposing air resistance. Read the question carefully. Go back to Question 1 Question 1Question 1

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Question 2 The balloon of weight 500 N (mass 50 kg) moves downwards with a constant velocity of 2m/s. Assume the only other force acting on the object is the air resistance. What is the magnitude of the air resistance ? What is the magnitude of the air resistance ? A. 0 NA. 0 N B. 100 N B. 100 N A. 0 NB. 100 N C. 50 NC. 50 N D. 500 N D. 500 N C. 50 ND. 500 N

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Option A The question asks for the opposing air resistance and not the resultant force. Read the question carefully. Go back to the Question 2 Question 2Question 2

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Option B The acceleration is not 2m/s 2. The balloon is moving with constant velocity of 2 m/s. Hint : What is the acceleration of an object with constant velocity? Go back to Question 2 Question 2Question 2

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Option C Mass is not a force. Weight is a force!!!! Go back to Question 2 Question 2Question 2

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Option D You are right!!! The balloon is moving with constant velocity and the resultant force is 0 N. Consider upwards as positive Air resistance – W = 0 Air resistance – 500 = 0 Air resistance = 500 N (Take note that Weight is a force but not mass). Go to question 3 question 3question 3 W = 500 N Air resistance

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Question 3 A car of mass 800 kg is being driven along a level road. The engine supplies a driving force of 3600 N and the resistive force is 2000 N. What is the acceleration of the car? 2000 N 3600 N A.2.0 m/s 2 B. 2.5 m/s 22.0 m/s 22.5 m/s 2 B. 4.5 m/s 2 C. 7.0 m/s 24.5 m/s 27.0 m/s 2

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Option A You are right!!! Consider left as positive. Let the acceleration be a. Resultant force = 3600 N + (-2000 N) = 1600 N Resultant force = mass x acceleration = 800 a 800 a = 1600 a = 2 m/s 2 Go to Question 4 Question 4Question 4 2000 N 3600 N Left as positive

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Option B There are two forces (resistive and a forward force) acting on the object. The resultant force is not 2000 N (resistive force) Remember : Resultant force = mass x acceleration Hint : Find the resultant force Go back to Question 3 Question 3Question 3 2000 N 3600 N

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Option C There are two forces (resistive and a forward force) acting on the object. The resultant force is not 3600 N (forward force) Remember : Resultant force = mass x acceleration Hint : Find the resultant force Go back to Question 3 Question 3Question 3 2000 N 3600 N

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Option D There are two forces (resistive and a forward force) acting on the object. The resultant force is not 5600 N as the two forces are acting in the opposite direction Remember : Resultant force = mass x acceleration Hint : Find the resultant force Go back to Question 3 Question 3Question 3 2000 N 3600 N

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Question 4 The car has mass 800 kg. The combined forces of friction and air resistance is 400 N and the acceleration (to the left) is 0.4 m/s 2. What is the forward driving force ? Forward driving force friction Air resistance A. 320 NB. 400 N 320 N400 N B. 480 N C. 720 N480 N720 N

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Option A The questions asks for forward force not the resultant force!!! The is more than 1 force acting on the car and the resultant force is not equal to the forward force!!! Read the question carefully. Go back to Question 4 Question 4Question 4 Air resistance Forward force Left as positive friction

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Option B The resultant force is not 0 !!! The car is accelerating (to the left) at a rate of 0.4 m/s 2 Go back to Question 4 Question 4Question 4 Air resistance Forward force Left as positive friction

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Option C The acceleration is to the left !!! Read the question carefully. Go back to Question 4 Question 4Question 4 Air resistance Forward force Left as positive friction

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Option D You are right!!! Consider left as positive. Resultant force = Forward Force + (-400N) = Forward Force - 400 Resultant force = mass x acceleration = 800(0.4) = 320 N Forward Force - 400 = 320 N Forward Force = 720 N Left as positive Air resistance Forward force Next

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Now for the more challenging questions!!! Now for the more challenging questions!!! Please proceed to do the Chpt 3 Dynamics Worksheet Pg 3 (Question 3 – 8) Please proceed to do the Chpt 3 Dynamics Worksheet Pg 3 (Question 3 – 8) Next

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