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2. Chapter 3: Forces Unit 1: Energy and Motion Table of Contents 3.3: The Third Law of Motion 3.1: Newton’s Second Law 3.2: Gravity 3

30. 3.1 Section Check Question 1 A. acceleration B. momentum C. speed D. velocity Newton’s second law of motion states that _________ of an object is in the same direction as the net force on the object.

31. 3.1 Section Check Answer The answer is A. Acceleration can be calculated by dividing the net force in newtons by the mass in kilograms.

32. 3.1 Section Check Question 2 A. joule B. lux C. newton D. watt The unit of force is __________.

33. 3.1 Section Check Answer The answer is C. One newton = 1 kg · m/s 2

34. 3.1 Section Check Answer Friction results from the sticking together of two surfaces that are in contact. Question 3 What causes friction?

68. 3.2 Section Check Question 1 Gravity is an attractive force between any two objects and depends on the masses of the objects and the distance between them. Gravity is an attractive force between any two objects and depends on __________. Answer

69. 3.2 Section Check Question 2 A. gravity B. net C. strong nuclear D. weak nuclear Which is NOT one of the four basic forces?

70. 3.2 Section Check Answer The answer is B. The fourth basic force is the electromagnetic force, which causes electricity, magnetism, and chemical interactions between atoms and molecules.

71. 3.2 Section Check Question 3 A. F = G(m 1 m 2 /d 2 ) B. G = F(m 1 m 2 /d 2 ) C. F = G(m 1 - m 2 /d 2 ) D. F = G(d 2 /m 1 m 2 ) Which of the following equations represents the law of universal gravitation?

72. 3.2 Section Check Answer The answer is A. In the equation, G is the universal gravitational constant and d is the distance between the two masses, m 1 and m 2 .

85. 3.3 Section Check Question 1 According to Newton’s law, the second object exerts a force on the first that is equal in strength and opposite in direction. According to Newton’s third law of motion, what happens when one object exerts a force on a second object? Answer

86. 3.3 Section Check Question 2 A. mass, acceleration B. mass, velocity C. mass, weight D. net force, velocity The momentum of an object is the product of its __________ and __________.

87. 3.3 Section Check Answer The correct answer is B. An object’s momentum is the product of its mass and velocity, and is given the symbol p .

88. 3.3 Section Check Question 3 When two objects collide, what happens to their momentum?

89. 3.3 Section Check Answer According to the law of conservation of momentum, if the objects in a collision exert forces only on each other, their total momentum doesn’t change, even when momentum is transferred from one object to another.

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91. End of Chapter Summary File