University Physics (Mechanics) Lab reports (assignment request: Friction) using a virtual physics labs (KET Simulation) as guided in the attached assignment instructions files. Below is the detailed log-in information for the KET Simulation for expert's access, download and installation link.
I am not reachable on call due to military mobilization.
https://virtualphysicslabs.ket.org/my-account/view-order/31303/
Log in username: olowoyos
Log in password: D@rksail0rd
Go to order# 31303 (First Semester Bundle)
Click on VPL-firstsemester.zip, download and install on expert's computer system for lab simulation.
Follow instructions for lab report criteria and assignment submission rubic on the lab manual and template attached. Please "submit using the lab template (Microsoft word) and delete all statements in red", vet solutions for plagiarism and submission deadline are to be strictly adhered to as required.
Microsoft Word - PHY 122 Friction.docx ASUonline PHY 122 Physics Laboratory Manual Page 1 of 6 FRICTION Introduction and Theory When two bodies are in direct contact, the interaction forces between their surfaces are called contact forces. There are two kinds of contact forces: the normal force – a force perpendicular to the contact surface, and the force of friction - a force parallel to the contact surface. Experiments show that a body moving on a horizontal surface slows down and finally stops. That means there is a force acting on the moving object in the direction opposite its motion and parallel to the contact surface. That force is called frictional force. We distinguish between two types of friction: static (for objects at rest) and kinetic (for objects in motion). Frictional forces are very complicated, however we can apply a simplified model according to which the maximum value of the force of static friction fs,max and the value of the force of kinetic friction fk are proportional to the magnitude of the normal force N acting between the two surfaces: fs,max = µs N (1) where µs is called the coefficient of static friction. That means in a particular situation fs ≤ µs N; fk = µk N (2) where µk is called the coefficient of kinetic friction. From everyday experience we know that on a horizontal surface, a larger force is required to make an object move than is required to keep it moving at a constant velocity (Fig. 1). 3. at rest: fs = T1 4. in uniform motion fk = T2 < t1="" fig.="" 1.="" forces="" acting="" on="" the="" box="" at="" rest="" (a)="" and="" in="" motion="" (b)="" on="" a="" horizontal="" surface:="" t="" is="" the="" rope="" tension="" force;="" fs="" -="" static="" friction="" force;="" fk="" -="" kinetic="" friction="" force;="" fk="">< fs,="" max.="" you="" must="" overcome="" the="" maximum="" static="" frictional="" force="" to="" make="" the="" object="" move,="" but="" once="" this="" is="" accomplished,="" you="" need="" only="" to="" balance="" the="" kinetic="" frictional="" force="" (which="" is="" smaller="" than="" the="" maximum="" static="" frictional="" force)="" to="" keep="" the="" object="" moving="" at="" a="" constant="" velocity.="" the="" coefficient="" of="" friction="" changed="" from="" static="" to="" kinetic="" the="" moment="" you="" exceeded="" the="" maximum="" static="" frictional="" force.="" the="" coefficient="" of="" static="" friction="" is="" the="" slope="" of="" a="" linear="" graph="" of="" frictional="" force="" versus="" normal="" force="" (figure.="" 2).="" notice="" that="" the="" force="" of="" static="" friction="" can="" take="" on="" a="" range="" of="" values="" from="" zero="" to="" its="" maximum.="" this="" is="" an="" important="" difference="" between="" static="" and="" kinetic="" friction="" since="" kinetic="" friction="" can="" have="" only="" fixed="" value.="" the="" coefficient="" of="" static="" friction="" is="" always="" larger="" than="" the="" coefficient="" of="" kinetic="" friction.="" t1fs="" t2fk="" t1="" =""> T2 ASUonline PHY 122 Physics Laboratory Manual Page 2 of 6 Fig. 2. A graph of the friction force magnitude f as a function of the applied force F. Let’s consider an object resting on the incline plane (Figure. 3). Figure. 3. Free body diagram on incline plane. According to Newton’s Second Law, if the object is not accelerating then the net force acting on it must be zero. The forces acting on the block are: normal force – N; the force of friction – f and the gravity force W = Mg. From the free body diagram (Figure. 3) you can see that an object can be at rest if the net forces at the directions parallel and perpendicular to the incline are both zero, e.g. fs = Mgsinθ and N = Mgcosθ (4) As we start increasing the incline angle θ, the friction force will increase as well, until we reach some critical angle θc, when there will not be equilibrium anymore and the body will start sliding downhill. At that moment the force of static friction has reached its maximum value fs, max, which must be equal to downhill force at that critical angle: fs, max = Mgsinθc. Taking into account that force of friction fs = µs N = µs Mgcosθ we have Mgsinθc = µs Mgcosθc, or µs = tanθc (5) Using equation (4) you will be able to calculate the coefficient µs of static friction by measuring the critical angle θc of the incline. Mgsinθ θ f θ Mgcosθ Mg N ASUonline PHY 122 Physics Laboratory Manual Page 3 of 6 In this lab you will measure the coefficients of static and kinetic friction forces for a cart (with the friction pad ON) in contact with the track. Objectives: Ø To apply friction force concept in different situations of the experiment and calculate coefficients of static and kinetic friction forces. Ø To explore the distinction between static and kinetic friction. Equipment: (Virtual) VirtualPhysicsLabs environment: friction cart, horizontal dynamic track with pulleys, strings, hanger, masses and ultrasonic motion detector; Logger Pro software. Procedure: Open KET simulation "Dynamics". Run the "Dynamics" lab. PART 1. Static Friction 1a) Cart on the horizontal track. Start up the Dynamics Track apparatus. Make sure the track is leveled (press “Set Θ = 0°”). Select “friction pad” (default is “wheel”). Set the µKS? # stepper to zero (you will see µk = 0.12 and µs = 0.18 by default). Put an extra 400 gram mass on the cart. Add a string and a mass hanger on the right side of the cart. The cart doesn’t move – it’s in equilibrium. Turn Dynamic Vectors ON, by clicking on the vectors’ box located above the masses, to see the forces acting on the cart. There are four vectors shown acting on it. Horizontally, the tension (T), pulls the cart to the right and the static force of friction (fs ) pulls it with equal force to the left (Figure. 4). Vertically, there are two forces: the gravity force which equals to the weight of the cart (Wc = Mg) is going downwards and the normal force (N ) opposed to it. The hanger also has a pair of forces acting on it. The upward tension force (T) is balanced by an equal, downward gravity force which equals to the weight of the hanging mass (Wh). Now start sequentially adding small masses (in steps of 10 grams) to the hanger until the
system starts moving. Record the total weight of the hanger (mass of the hanger plus all additional masses). (Hint: If you are not certain how many masses are on the hanger, make the right click to use the Zoom In tool). At the moment of movement tension force equals to the maximum static friction force between the cart and the track T = fs, max = µs N . The tension in the hanger equals to its weight T = Wh= mh g Combining these two equations the one can solve for µs. The calculated value of µs needs to be compared with the given coefficient of static friction (µs = 0.18) by calculating the discrepancy: ASUonline PHY 122 Physics Laboratory Manual Page 4 of 6 Fig. 4. Free body diagram of the system. 1.b) Cart on an Incline plane. Start up the Dynamics Track apparatus. Set the µKS? # stepper to zero (µk = 0.12 and µs = 0.18 by default). Please notice that the dynamic track has a feature to be tilted by dragging when the mouse cursor is in the colored part of either end of the track. The message box informs that the track can be tilted up or down. With the brake off, turn on the friction pad and put 400 grams mass on the cart. The string, pulley and hanger are not needed for this part of the experiment. The free body diagram for an object on an incline plane is given in Figure. 3. Keep the Dynamic Vectors ON, by clicking on the vectors’ box located above the masses, to see the forces acting on the cart. Now start increasing the incline angle θ by small increments (the static friction force will increase as well as can be seen on the force diagram), until you reach some critical angle θc when the cart starts sliding downhill. Repeat the experiment to read a more accurate value for θc. At that angle the static friction force has reached its maximum value. Use formula (4) to calculate the coefficient of static friction. Compare your calculated value with the given one (which is given in the control box for µS (0.18)) by calculating the discrepancy: 100%* (|calc. value– expect. value| / expect. value). PART 2. Kinetic friction 2a) Cart on the horizontal track You just verified that static friction varies from zero to some maximum amount (fs,max ) (0 ≤ fs ≤ fs, max). If you exert a horizontal force greater than fs, max the object will accelerate. On the other hand kinetic frictional force (fk ) is a fixed value between the surfaces of two objects and it is always less than fs, max. Therefore, • When an object is at rest, the friction force is ≤ fs, max. • When an object is moving, the friction force equals fk. As it was described in the introduction if you pushed the box until it began to move, you could then back off and push it with a smaller (than fs, max) force and the box would continue to move (Figure. 2). That is what the “Bump” does (see in the control box). It gives the cart a tiny velocity to break it free; then the cart can move against the force of kinetic friction. You are going to observe this behavior and see how fk responds when various forces act on the body. Tfs Wc N T Wh ASUonline PHY 122 Physics Laboratory Manual Page 5 of 6 Start up the Dynamics Track apparatus. Make sure the track is leveled (press “Set Θ = 0°”). Remove all the masses used in part 1 – Reset All. Put extra 320 gram mass on the cart. Turn the friction pad on . Click “Brackes Off “ button