FORCE AND NEWTON’S LAWS REVIEW

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FORCE AND NEWTON’S LAWS REVIEW Open Forces and Motion Basics Part I - Newton’s First Law Choose the “Motion” window to start the simulation Make sure the boxes that say “Force”, “Values” and “Speed” are checked! a. Apply a force of 50 N right to the box. Describe the motion of the box using physics terms (i.e. velocity, acceleration, displacement). Refer to the speedometer in your answer. The box to the right experiences motion that is characterized by changes in acceleration, displacement, and velocity when a force of 50 N is applied to it. When the box is initially at rest, it accelerates in the direction of the given force, which causes its velocity to gradually grow. The speedometer's measurements, which show the amplitude and direction of the box's motion, show that the box's velocity increases gradually as long as the force is present. Simultaneously, the box's displacement, or change in position, advances in the direction of the applied force, signifying the distance the box travels along its trajectory. Overall, the box's motion can be explained as its dynamic reaction to an applied force, with variations in displacement, acceleration, and velocity indicating how outside forces have affected the box's path. b. Reset the scenario (don’t forget to check forces, speed again). Apply a force of 50 N to the right for about 5 seconds then reduce the applied force to zero (the man should stop pushing). Don’t reset the scenario. Describe the motion of the box. Refer to the speedometer in your answer. The box moves in a certain way after being pushed right for about five seconds with a force of fifty Newtons applied, and then it stops moving altogether. In the beginning, the box accelerates in the force's direction as it is applied, increasing its velocity gradually. The speedometer readings, which display a gradual increase in speed during the course of the force application, indicate this acceleration. Nevertheless, because there is no external force working on the box to maintain or increase its velocity, it gradually decelerates as it moves ahead due to inertia when the applied force is reduced to zero. If there are no other external forces at play, the speedometer readings will eventually show a drop in speed as the box decelerates and comes to a stop. This behavior is consistent with Newton's First Law of Motion, which states that unless an outside force acts against an item in motion, it will continue to move at a constant speed. c. Apply a force of 50N to the left. Describe the motion of the box.

The box responds in kind to a force of 50 N applied to its left in terms of motion. The force causes acceleration or deceleration in the opposite direction from the box's initial motion since it is directed in the opposite direction. The force would operate as a braking force if the box was initially at rest or moving to the right; if the force continues, the box would slow down or eventually come to a stop. In contrast, acceleration would result from the force acting in the same direction as the box's initial motion if it had been traveling to the left. In either case, how much force is applied would dictate how quickly the box accelerates or decelerates. d. Explain the exact steps needed to make the box come to a stop. To bring the box to a stop, first, assess its direction of motion. Then, apply a force in the opposite direction of its motion, ensuring it's of sufficient magnitude to counteract the box's momentum. Monitor the box's motion closely, adjusting the applied force as needed to achieve a gradual deceleration. Once the box has slowed down significantly, continue applying the force until it comes to a complete stop. Finally, cease the applied force to prevent any further motion. This sequence of steps ensures a controlled and safe deceleration, effectively halting the box's movement. Summary Newton’s First Law of Motion States “An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.” Explain how your observations in a - d support this Law. Newton's First Law of Motion, which states that an object at rest will remain at rest and an object in motion will continue to travel with constant velocity in a straight line unless acted upon by an external force, is completely aligned with the observations in sections a through d. In portion a, the box begins to move from a resting position when a force of 50 N is applied, indicating the necessity of an external force to change its motion. The effects of external forces on the box's motion are further demonstrated in parts b and c, where the box experiences acceleration or deceleration depending on the direction and magnitude of the applied forces. The box finally comes to a stop in section d when a force is applied in the opposite direction of its motion, demonstrating how an unbalanced force may overcome the box's inertia and alter its motion. According to Newton's First Law of Motion, these observations offer precise illustrations of how outside forces affect an object's motion .

Part II - Newton’s Second Law a. Reset the sim, don’t forget to check force, values and speed again. Remove the box and place a garbage can on top of the skateboard. Using your timer/phone, measure the amount of time it takes to reach maximum speed using a force of 50 N. Try this again with forces of 100N, and 200N. Applied Force (N) Time To Max Speed (s) 50 1 minute 18.63s 100 39.35s 200 18.48s b. Reset the sim, check force, values, speed and the masses boxes this time. Set the applied force to 200 N Right. Using your timer/phone measure the amount of time it takes to reach maximum speed. Repeat with two crates, one crate and a garbage can, and a refrigerator. Record your findings! Object – Mass (kg) Time To Max Speed (s) 50 1 minute 18.82s 100 19.26s 150 22.40s 200 36.97s Using MS Excel, create a graph of time vs mass. Sketch this graph in the space below. Recall how acceleration is related to time. Note: In this case the final speed of all the trials is the same. Manipulate your time data to get an appreciation for how the acceleration of the mass changes in each trial. Sketch an acceleration vs mass graph using this data in the space below (you can use MS Excel).

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Summary Newton’s Second Law states “The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.” Explain how your observations in both a and b support this Law. Newton's Second Law of Motion is firmly supported by the observations in both sections a and b. In section a, the box accelerates in the force's direction when a force of 50 N is applied to it. The acceleration of the box rises with increasing force, in a direct proportion to the applied force. This is in complete accordance with the law, which states that an object's acceleration is directly proportional to the strength of the net force. Furthermore, in section b, the acceleration that results varies in accordance with changes in the force applied and the box's constant mass of 50 kg. As the mass grows for a given force, the acceleration falls, illustrating the inverse relationship between acceleration and mass. All things considered, the findings in parts a and b offer convincing proof of the ideas presented in Newton's Second Law of Motion. Part III - Friction’s Effects The behavior of the skateboard in Part I and part II were not very realistic because friction was not present. At the bottom of the screen is a simulation that includes friction. Select this simulation. a. Set friction to “none”. Notice how the screen changed. Why do you think the app designers did that?

Any resistance or opposing force that would normally operate on objects within the simulation is probably removed when friction is set to "none". This feature was probably added by the app makers to enable users to learn physics in idealized settings where friction is either nonexistent or very small. With friction removed, users can better isolate and comprehend the impacts of other forces, which might be advantageous for instructional reasons. It also gives users the freedom to experiment with various settings and see how friction affects moving items' behavior. All things considered, the ability to set friction to "none" improves the simulation's adaptability and instructional value. b. Make sure that only speed box is checked. i. Apply a force to get the box to about half of it’s maximum speed, then remove the force. ii. While the box is moving, move the friction slider to 1/2 way. What happened to the box? Due to its inertia, the box will keep moving forward even if a force is given to it until it reaches around half of its maximum speed and then withdrawn. Nevertheless, the friction exerted on the box increases when the friction slider is shifted halfway while the box is still moving. The box eventually slows down as a result of the increased friction acting as a resisting force against its motion. The box consequently moves more slowly and, if the friction force is sufficient to overcome its inertia, eventually stops. Overall, the box will slow down and eventually decelerate if the friction slider is adjusted halfway while it is moving. Summary Is friction a force? What evidence do you have? Friction is a force, yes. There are several types of evidence to back up this statement. First of all, as we try to move objects across surfaces in our daily lives, we may observe the impacts of friction. A force opposing motion is shown by resistance experienced while moving objects or heat produced when rubbing surfaces together. Second, measurements of the force needed to overcome friction and observations of its effects under various conditions have allowed experimental investigations in physics to provide verifiable proof of frictional forces. Last but not least, friction is well-established theoretically within the context of classical mechanics. The link between frictional force, the normal force between surfaces, and the coefficient of friction is described by mathematical models like Coulomb's law of friction. The convergence of experimental, theoretical, and observational data demonstrates that friction is, in fact, a force that is essential to the dynamics of objects in contact.

Part IV - Back to Newton’s Second Law Reset the Friction app. Make sure Forces and Speed are checked. a. Apply a force of 50 N. Describe the movement of the box. The box moves in the direction of the applied force when 50 N is applied to it. In reaction to the imparted force, the box steadily accelerates, progressively increasing its velocity over time. The box is moving steadily along its path as a result of this motion, which is defined by a constant acceleration in the direction of the force. b. Apply a force of 100 N. Describe the movement of the box. When 100 N of force is applied to the box, the movement is more noticeable than in the case of 50 N. In reaction to the increased force, the box accelerates and increases in velocity more quickly. In comparison to the 50 N scenario, this causes the box to move faster and cover a greater distance in the same amount of time. c. Apply a force of 150 N. Describe the movement of the box. 150 N of force is applied to increase the box's movement even more. In comparison to the earlier cases, the acceleration is significantly more significant, resulting in a faster increase in velocity. In comparison to the 100 N scenario, this means that the box travels even faster and covers a bigger distance in the same amount of time. d. Check the box that says “Sum of Forces”. Repeat procedures a, b, and c. What was different about c? 150 N of force is applied to increase the box's movement even more. In comparison to the earlier cases, the acceleration is significantly more significant, resulting in a faster increase in velocity. In comparison to the 100 N scenario, this means that the box travels even faster and covers a bigger distance in the same amount of time. Summary Newton’s Second Law states “The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force , and inversely proportional to the mass of the object.” Explain how your observations relate to the underlined portion of this Law (hint, you might want to look up the definition of the word “net”). According to Newton's Second Law, the net force—that is, the total of all forces operating in the same direction—directly affects an object's acceleration. According to the given observations, the applied force determines the acceleration of the box by acting as the net force acting on it. The acceleration of the box increases proportionately as the applied force increases from 50 N to 100 N and 150 N, demonstrating the direct correlation between acceleration and net force magnitude. Furthermore, the data demonstrate the

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inverse relationship between mass and acceleration, with acceleration falling off when the box's mass stays constant but the applied force changes. Thus, the data provide evidence in favor of Newton's Second Law by showing that an object's acceleration is directly influenced by the amount of the net force acting in the same direction as the force applied, whereas an object's mass has an inverse effect on acceleration. Part V: Friction in Detail a. Reset the app. Check the force and speed box. Apply 50 N of force to the crate. Slowly click (in 50 N increments) to increase the amount of applied force until the crate starts to move/accelerate. Note the range of force values when the crate first started to move. Record this range below (e.g. starts moving somewhere between 0 and 50 N). The range of force values when the crate first starts to move is between 0 and 50 N. b. Reset the app. Repeat the steps in “a”. Once you have just made the crate move do not adjust the force any higher. Allow the block to move with this constant force for 2.0 seconds. Now reduce the force by 50 N. How does the crate behave immediately after reducing the force by 50 N? Did it keep accelerating? Move at a constant speed or decelerate? Does this behaviour surprise you based on your knowledge of Newton’s 1 st and 2 nd Law. Why do you think the crate behaves this way? Depending on whether opposing forces, like friction, are present or absent, the box responds differently to a force reduction of 50 N. Even when the force is reduced, the crate will accelerate continuously if friction is minimal or nonexistent. This behavior is consistent with Newton's First Law since, absent an outside force, the crate will usually continue in its current velocity. But, if friction is high, it will resist the crate's motion and cause it to gradually slow down as the force is released. This action is consistent with Newton's Second Law because, in the event of opposing forces, the net force acting on the crate diminishes following the force reduction, leading to a decrease in acceleration or deceleration. Overall, the crate's behavior after the force was reduced by 50 N illustrates how variations in applied force and opposing forces affect an object's motion, so reflecting the fundamental ideas of Newton's Laws of Motion. c. Reset the app. Check the speed, force, sum of forces and values boxes. Adjust the value of the applied force using single Newton increments to determine the exact force required to make the crate move. Mentally note the value of this force so you can record it after in the space below. Now keep increasing the value of the applied force in large 50 N or small single Newton increments. What happens to size of the friction force? What is the value of the friction force now? Why does the friction force behave this way?

The friction force initially stays constant until the applied force surpasses the maximum static friction force, at which point it is gradually increased to find the threshold force needed to move the crate. The friction force changes to kinetic friction once the crate moves, usually at a somewhat lower magnitude than static friction. That means that if the crate speeds, the friction force will also likely increase significantly to keep equilibrium as the applied force keeps rising. The opposing motion or tendency of motion between the surfaces in contact is the reason for the friction force's behavior. Kinetic friction opposes motion once it is initiated, while static friction initially hinders motion until it is overcome. The coefficient of friction between the surfaces and the normal force forcing them together are two examples of variables that will affect the exact value of the friction force. d. Repeat step c and after the block has accelerated for 3.0 seconds reduce the applied force to 0 N. What happens to the size of the friction force after the applied force goes to 0 N? How does the crate behave? If the crate keeps moving at the same speed after the applied force is lowered to 0 N after 3.0 seconds of acceleration, the friction force's magnitude stays constant. This is due to the fact that once motion is started and the surfaces stay in contact, kinetic friction—which works to prevent the crate from moving—usually stays constant. Therefore, the friction force will balance out any other forces acting on the container, like air resistance or inertia, as long as it maintains a consistent velocity, allowing it to continue moving. However, kinetic friction acts to decelerate the container until it achieves a state of equilibrium, thus if the crate stops because there are no external forces acting on it, the friction force will gradually bring it to rest. All things considered, the way the crate behaves when the applied force is reduced to 0 N shows how kinetic friction helps to keep or slow down motion. e. Reset the app. Check the forces, values and speed boxes. Place another crate on top of the first. Determine the minimum amount of force required to move the crates. Determine the minimum amount of force required to keep the blocks moving at a constant speed. Record these below: i. How do these values compare to the values found for one crate? What does this tell you about the affect of mass on friction?

The system's overall mass rises when a second crate is stacked on top of the first. Because of this, moving the boxes will probably demand more force than it did when there was only one crate. This is due to the fact that greater mass causes a higher inertia, which needs to be overcome with greater power in order to start motion. Similarly, with the additional mass, there will probably be a greater minimum force needed to maintain the blocks' constant speed. This is due to the fact that the extra mass increases the system's gravitational pull and, as a result, the force of friction that prevents mobility. As a result, greater effort is required to offset these conflicting forces and keep the speed constant. This analogy emphasizes how mass affects friction. The frictional force preventing motion grows with mass, necessitating a stronger force to overcome it. As a result, the force required to overcome friction and maintain motion is directly influenced by the mass of an item or system. f. Reset the app. Check the force and values boxes. Apply 50 N of force to the crate. What is the value of the force of friction now? Record this. Increase the applied force and note how the friction force behaves. Record this behaviour in the space below. Assuming the crate is in motion and experiencing kinetic friction, the force of friction when 50 N of force is applied to it is usually equal to the force applied. When static friction is present and the crate is stationary, the crate will start to move when the applied force reaches the maximum static friction force. Static friction works by matching the applied force. If the crate accelerates, the friction force may also rise to match the applied force and preserve equilibrium when the applied force increases beyond 50 N. Summary Make four or more general statements about the force of friction based on your observations in parts a – f. 1. The force of friction works as a resistive force to prevent or slow down motion by opposing the motion or propensity of motion between two surfaces in contact. 2. The type of the surfaces in contact and the normal force pressing them together determine the size of the friction force; rougher surfaces and higher normal forces typically result in bigger friction forces. 3. When motion is began, friction between stationary surfaces changes to kinetic friction, which tends to be generally constant as long as the surfaces stay in contact and the applied force stays constant. Static friction might fluctuate depending on the applied force.

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4. Friction acts as a counteracting force to limit an object's acceleration and as a resistive force that opposes motion to cause changes in the object's velocity, either accelerating or decelerating.

FORCE AND NEWTON’S LAWS REVIEW

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