Force and Motion Study Guide Answer Key

Force and Motion Study Guide-ANSWER -ANSWER K KEY EY Name: Period: Date: Define th thee follow following ing tter er erms: ms: 1.) energy: the capacity to do work or the ability to cause motion 2.) potential energy: is stored energy or energy of position that is waiting to be released. 3.) kinetic energy: is energy of motion 4.) speed: is the distance an object travels in a certain amount of time 5.) force: is a push or pull on an object 6.) mass: the amount of matter in a an object 7.) weight: the gravitational pull on an object 8.) acceleration: the change in speed divided by time 1 1/9 Define th thee follow following ing tter er erms: ms: 9.) inertia: is the resistance of an object to change its motion 10.) Newton’s First law: An object at rest will stay at rest unless acted on by an unbalanced force. An object in motion will stay in motion at the same speed and in the same direction unless acted n by an unbalanced force. 11.) friction: A force that exists at the boundary between any two pieces of matter that are in contact with each other. 12.) Newton’s Second law: The acceleration of an object by a force is inversely proportional to the mass of the object and directly proportional to the force. 13.) Newton’s Third law: For every actin, there is an equal but opposite reaction. 14.) center of mass: The point where the distribution of an object’s mass is balanced 15.) deceleration: Stopping or slowing motion. Answ nswer er th thee follo follow wing qquestions: uestions: 16.) Any object’s speed can be calculated by dividing the distance traveled by the time taken. (E-74) 2 2/9 Answ nswer er th thee follo follow wing qquestions: uestions: 17.) The formula for speed is: Speed = distance time (E-74) 18.) Calculate the speed for the following problem: A motorcycle traveling the distance of 400 meters in 16 seconds is traveling at what speed? (show all work and use correct units of measurement) (E-74) Speed = distance ÷ time Speed = 400 m ÷ 16 s Speed = 25 m/s 19.) Explain what is happening in each graph below: (E-75) a.) b.) Balanced Zero Net Force Traveling at a constant speed and in the same direction. c.) • Balanced • Zero Net Force • Traveling at a constant speed and In a constant but opposite direction d.) Unbalanced • Unbalanced Nonzero Net Force • Nonzero Net Force Move in a constant spped in the same direction, then • Acceleration stops, and then moves at a constant speed in the same direction. 3 3/9 Question 19 (con (continued) tinued) e.) f.) Unbalanced Nonzero Net Force First moves at a constant speed and in the same direction, then stops, and then moves at a constant speed and in the same direction again. • Unbalanced • Nonzero Net Force • Deceleration 20.) What does the change in slope of a motion graph indicate? (E-75) The change in slope means that there is a change n direction, speed, or in both. 21.) A force is what changes the motion of an object. (E-76) 22.) What is the unit of measurement for acceleration? (E-78) meter / second / second (m/s2) 23.) What is the unit of measurement for force? (E-78) Newtons (N) 24.) Inertia describes the tendency of an object to continue moving at the same speed and in the same direction . (E-79) 25.) The more mass and object has, the more inertia it has, and the greater the force it takes to change its motion . (E-79) 4 4/9 26.) Explain what you learned about inertia from your “Inertia Around A Curve Lab.” Make sure you include information about the affect each different opening of the ring had on inertia and the affect mass (each marble) had on inertia in your explanation. (E-79) Regardless of the opening size of the ring and regardless of the mass of the marble, once the marble reached the opening, it traveled in its natural state closest to the state of inertia which was in a straight path since no force was acting on the marble. 27.) Imagine that a car is approaching a curve in the road when it suddenly loses its steering and brakes. The area is flat and there is a guardrail on the road. a.) Draw a line showing the car’s path in the diagram below. (E-79) Guardrail b.) Explain why the car will take that path: The car will curve and not follow the path of inertia because the guardrail is a force acting on the car to make it change direction. 5 5/9 28.) Who wrote the laws of motion and how many laws are there? (E-80) Isaac Newton and he wrote 3 laws. 29.) A change in motion can be a change in an object’s speed , direction , or both . (E-80) 30.) Newton’s first law states that an object’s motion cannot change unless a force acts on the object. (E-80) 31.) It takes a force to overcome an object’s inertia and to make the object go faster, slower or change direction. (E-80) 32.) Which has more inertia: a bowling ball or a golf ball rolling at the same speed in the same direction? Explain your answer. (E-80) Newton’s first law states: An object at rest will stay at rest unless acted on by an unbalanced force. An object in motion will stay in motion at the same speed and in the same direction unless acted n by an unbalanced force. A bowling ball has more inertia because it would take more force to change its motion than it would take to change the golf ball’s motion. 33.) If there were no friction, the inertia of a moving object would keep it moving the same way forever or until a force changes its motion. (E-80) 34.) What would happen to Mrs. Everett if you could throw her in outer space? Explain in terms of inertia and friction. (E-80) Newton’s first law states: An object at rest will stay at rest unless acted on by an unbalanced force. An object in motion will stay in motion at the same speed and in the same direction unless acted n by an unbalanced force. Mrs. Everett would continue to travel in a straight line and at a constant speed forever because there is no friction in outer space, therefore, Mrs. Everett would travel in a state of inertia. The only way Mrs. Everett could change her direction or speed is if she encountered another force that changed her motion. 6 6/9 35.) Define net force: (E-80) Net force: the combined force acting on an object 36.) Draw a diagram of a balanced force. Then below the diagram define its net force and acceleration. (E-81) 5.0 N 5.0 N Net Force = 5.0 N- 5.0 N = 0 N Acceleration: There is no acceleration because the object did not move. 37.) Draw a diagram of an unbalanced force. Then below the diagram define its net force and acceleration. (E-81) 21.0 N 7.0 N Net Force = 21.0 N– 7.0 N = 14.0 N Acceleration: There is acceleration because the object moves to the left. 7 7/9 38.) In each situation below, write “nonzero net force” or “zero net force.” Then explain the reason why the force is nonzero or zero. (E-81) a.) a bicycle parked on the sidewalk Zero Net Force, because the bicycle has no speed and is not changing its direction, and therefore, is no change in motion. b.) a train changing tracks at a constant speed Nonzero Net Force, because the train changed in direction which is a change in motion. c.) a person running on a tread mill at the speed of 6 MPH for 30 minutes Zero Net Force, because in that 30 minutes the runner never changed his speed or direction, and therefore, there is no change in motion. d.) at the beginning of a race, a track runner starts running at the sound of the whistle Nonzero Net Force, because the runner starts from zero speed to eventually reaching maximum speed which is acceleration, and therefore, is a change in motion. 39.) What is the equation for Newton’s second law? (E-80) F = ma 40.) A 50 kg skater pushed by a friend accelerates 5 m/s2. What is the force? Show your work and use the correct unit of measurement. (E-80) Force (N) = Mass (kg) x Acceleration (m/s2) Force (N) = 50 kg x 5 m/s2 Force = 250 N 41.) A bowling ball rolled with a force of 15 Newtons and accelerates at a rate of 3 m/s2. What is the mass of the bowling ball? Show your work and use the correct unit of measurement. (E-80) Force (N) = Mass (kg) x Acceleration (m/s2) 15 N = Mass (kg) x 3 m/s2 15 N ÷ 3 m/s2 = Mass (kg) x 3 m/s2 ÷ 3 m/s2 15 N ÷ 3 m/s2 = Mass (kg) 5 kg = Mass 8 8/9 42.) A person and a sled have a combined mass of 75 kg and are pushed with the force of 300 Newtons. What will be the acceleration in this problem? Show your work and use the correct units of measurement. (E-80) Force (N) = Mass (kg) x Acceleration (m/s2) 300 N = 75 kg x Acceleration (m/s2) 300 N ÷ 75 kg = 75 kg ÷ 75 kg x Acceleration (m/s2) 300 N ÷ 75 kg = Acceleration (m/s2) 4 m/s2 = Acceleration 43.) Newton’s third law states that when one object applies a force on a second object, the second object applies the same size force in the opposite direction, and for the same amount of time on the first object . Another way to think about this is that when one object pushes or pulls on another object the other object will always push or pull back with the same force. (E-80) 44.) Explain using Newton’s third law how it applies to a person sitting in a chair. (E-80) Newton’s third law states: The acceleration of an object by a force is inversely proportional to the mass of the object and directly proportional to the force. The person is exerting a force on the chair which is the action, and the chair is exerting an equal but opposite force on the person which is a reaction. 45.) Explain how the center of mass affects the stability of an object when an object has its center of mass at the top of the object? At the bottom of the object? (E-86) An object that has its center of mass at the top of it is less stable because it can easily be tipped over when a force is applied to it. The object with the center of mass at the bottom is more stable because it is less likely to tip over when a force is applied to it. 9 9/9