AP® Physics 1 2022 Scoring Guidelines Practice Exam 2 Question 1: Short Answer (a) 7 points Horizontal component: For a non-zero horizontal line 1 point Vertical component: For a non-vertical line with a negative slope that crosses the horizontal axis near t f 2 and reaches t f 1 point Scoring note: Any part of the sketched graph beyond t f is ignored. Total for part (a) (b) (i) For a gravitational force with correct direction and label 2 points 1 point 1 point For a tension force with correct direction and label Scoring note: A maximum of one point may be earned if there are any extraneous forces. (ii) For a vector pointing downward representing the gravitational force with no extraneous forces 1 point Scoring note: A label is not required, since the use of labels is assessed in part (b)(i). (iii) For attempting to find the horizontal component of velocity 1 point Scoring note: See examples below. This point is earned for the wrong use of trig functions if it is clear it is being used to find the horizontal component, but not awarded if it’s not clear which component the trig function is referring to, or for stating that the vertical component is zero. 1 point For a correct numerical answer for horizontal velocity with correct units Example response: 0 points: v sin θ = 13 m s (No clear indication of an attempt to find the horizontal component) 1 point: = vx v= sin θ 13 m s (An attempt to find the horizontal component is implied by the vx term) 1 point: v cos θ (An attempt to find the horizontal component is implied by the cos θ term) (Correct numerical answer with no units) 1 point: v cos θ = 7.5 1 point: 7.5 m s (Correct answer with units, but no work shown) 2 points: 15cos 60 = 7.5 m s (Correct answer with units) 2 points: 15cos 60 m s (Correct answer with units) Total for part (b) 5 points Total for question 1 7 points © 2022 College Board AP® Physics 1 2022 Scoring Guidelines Question 2: Experimental Design (a) 12 points For a valid statement relating the speed of cart and dissipation of mechanical energy 1 point Examples of valid statements: More damage when going faster Slower collision means compression and decompression during collision happen without permanent deformation Examples of invalid statements: Higher fraction of K is lost at higher speeds Because more kinetic energy is lost Total for part (a) (b) 1 point 1 point For measuring the speed of both carts before and after collision Scoring note: It is not necessary to measure the initial speed of the cart that is at rest. For measuring the mass of the carts (or calculating mass ratio using conservation of momentum, which may be stated later) 1 point For equipment and measurements consistent with procedure as described or drawn in diagram (e.g., motion detectors in the right places to measure speed of both carts) 1 point For varying the speed (making speed the independent variable) of the first cart in a feasible experiment that could be done in a school lab. 1 point Scoring note: “Varying the speed” means at least 2 trials (to test hypothesis), and “feasible” means that equipment is used appropriately for each measurement. For attempting to reduce uncertainty, e.g., multiple trials for a given initial speed of cart 1, or trials involving at least three different initial speeds © 2022 College Board AP® Physics 1 2022 Scoring Guidelines For attempting to reduce uncertainty, e.g., multiple trials for a given initial speed of cart 1, or trials involving at least three different initial speeds 1 point Example response: Quantity to be Measured Initial speed of heavy cart (H) Final speed of heavy cart Mass of heavy cart Final speed of light cart (L) Mass of light cart MS1 H Symbol viH vf H mH vf L mL Equipment for Measurement Motion sensor (MS1) Motion sensor (MS1) Triple beam balance Motion sensor (MS2) Triple beam balance L MS2 Measure the mass of each cart with the triple beam balance. Set the carts and motion sensors on the track. With the motion sensors recording, push the heavy cart toward the light cart so that they collide. Record the motion sensors readings for the speeds of the heavy cart immediately before the collision, and the speeds of both carts immediately after the collision. Repeat 8 times, varying the force with which the heavy cart is pushed so that a wide range of initial velocities for the heavy cart are used. Total for part (b) (c) 5 points For a correct indication of how initial and final total kinetic energy would be calculated from the raw data 1 point For using the difference between initial and final total kinetic energy to determine the kinetic energy lost 1 point For a description of how the calculated fractional energy losses would be used to confirm or disconfirm the hypothesis 1 point Example response: For each trial, calculate the initial kinetic energy of the heavy cart using Kinit = (1 2)mH viH 2 . (1 2)mH vf H 2 + (1 2)mL vf L 2 . Also calculate the final kinetic= energy K f K init Make a graph of K lost = ( K init − K f ) K init as a function of viH . If a positive trend is seen in the data, the hypothesis is confirmed. Total for part (c) 3 points © 2022 College Board AP® Physics 1 2022 Scoring Guidelines (d) 1 point For using momentum conservation to find v f in terms of vi , or the ratio of postcollision to pre-collision speed 1 point For a correct expression for final kinetic energy (or consistent with v f found from conservation of momentum) OR a correct expression for the fractional energy loss in terms of m1 , m2 , the initial speed of the heavy cart, and the final speed of the two-cart system 1 point A correct expression for fraction of kinetic energy lost: m2 m1 or 1 − m1 + m2 m1 + m2 Scoring note: The above point is not earned if the answer includes any variables other than m1 and m2 Total for part (d) 3 points Total for question 2 12 points © 2022 College Board AP® Physics 1 2022 Scoring Guidelines Question 3: Qualitative/Quantitative Translation (a) 12 points For an arrow directed upwards labeled Tension (or FT ) 1 point For an arrow directed downwards labeled Force of Gravity (or mg , or Fg ). 1 point Scoring note: G or g are not acceptable labels for the force of gravity 1 point For an arrow labeled tension that is larger than the arrow labeled Force of Gravity. Scoring note: a maximum of two points can be earned if there are any extraneous forces. Example response for part (a) Total for part (a) (b) 3 points For a sketch showing a non-linear path 1 point For a sketch that is concave up 1 point For a justification that addresses that the box is moving at a constant speed in the horizontal direction and accelerating in the vertical direction which leads to a concave up parabola. 1 point © 2022 College Board AP® Physics 1 2022 Scoring Guidelines Example response for part (b) Since the box is moving at a constant speed in the horizontal direction and accelerating in the vertical direction, the path that the box takes should look like a concave up parabola Total for part (b) (c) 1 point For a kinematic equation correctly relating the horizontal position of the box to the horizontal component of the speed of the box and the time vx = x t 0.5 m/s = t= 3 points x t x 0.5 m/s For a kinematic equation correctly relating the vertical position of the box as a function of the vertical acceleration of the box and the time 1 point 1 2 ayt 2 1 y = (1.0 m/s 2 ) t 2 2 y= 1 point For correctly combining the vertical and horizontal motions of the box into a single equation. 1 x y = (1.0 m/s 2 ) 2 0.5 m/s 2 y = ( 2 m −1 ) x 2 Total for part (c) 3 points © 2022 College Board AP® Physics 1 2022 Scoring Guidelines (d) For an attempt to use functional dependence to describe how the equation and the sketch in part B relate 1 point For using functional dependence correctly to relate the equation derived in part (c) consistently to the graph sketched in part (b). 1 point Example response for part (d) The equation I derived shows that the vertical position of the box is proportional to the horizontal position squared and so the shape of the path traveled by the box should be a parabola, as sketched in part (b). Total for part (d) (e) 2 points 1 point One point for an arrow pointing upwards and to the right. Example response for part (e) Total for part (e) 1 point Total for Question 3 12 Points © 2022 College Board AP® Physics 1 2022 Scoring Guidelines Question 4: Paragraph-Length Response (a) (b) 7 points For a labeled friction force vector in the correct direction in both diagrams 1 point For labeled gravitational and normal forces in the correct directions in both diagrams, with no extraneous forces Total for part (a) 1 point 2 points Correct Answer: tdown > tup Scoring note: The response is graded even if an incorrect selection is made. For stating that the magnitude of the net force on the block is greater when it is sliding up the ramp than when it is sliding down the ramp because the direction of the frictional force changes while the direction of the component of the gravitational force along the ramp does not (this can be implied) OR a description of the net force consistent with the free-body diagrams (FBDs) in part (a) 1 point For stating that the magnitude of acceleration of the block while sliding up the ramp is greater than that when sliding down, OR a description of acceleration consistent with the FBDs in part (a) 1 point For a justification that v f is less than v0 , OR average v up is greater than average v 1 point down (e.g., speed changes more on way up than on way down because acceleration is greater on the way up and the same distance covered and final/initial speed on way up/down is zero), OR a description of final and initial speeds consistent with the FBDs in part (a) For a correct argument that, if v f is less than v0 or average speed up is greater than 1 point average speed down, then tdown is greater than tup . (This argument could include a kinematic equation.) Scoring note: Student cannot earn this point even if justification is consistent with incorrect part (a) FBD For a logical, relevant, and internally consistent argument that addresses the required argument or question asked, and follows the guidelines described in the published requirements for the paragraph-length response 1 point Scoring note: A maximum of 4 of 5 points (first 3 points plus 5th point) can be earned if the FBD in part (a) is incorrect (e.g., friction force is in the same direction in both FBDs) © 2022 College Board AP® Physics 1 2022 Scoring Guidelines Alternate solution using work/energy reasoning for 1st two points of part (b) For correctly applying work-energy to up/down ramp (or, indicating block-Earth system has the same potential energy at the beginning and end) 1 point For correct treatment of energy loss to friction 1 point Total for part (b) 5 points Total for Question 4 7 Points © 2022 College Board AP® Physics 1 2022 Scoring Guidelines Question 5: Short Answer (a) 7 points 1 point For correctly relating the difference in maximum height of the ball to the kinetic energy of the ball before and after the collision. Example response for part (a) If the collision between the ball and the floor were elastic, the speed just before the ball hits would be equal to the speed of the ball just after it leaves the floor. Because of conservation of energy, since air resistance is negligible, if the speed before and after the collision were the same the ball should return to its starting height. Because it returns to a lower height, we must conclude that there was energy lost in the collision, making the collision inelastic. Total for part (a) (b) 1 point For using conservation of energy or work energy principle to attempt to find the speed of the ball just before the ball hits the force sensor. 1 point For using conservation of energy or work energy principle to attempt to find the speed of the ball just after the ball hits the force sensor. 1 point For correctly addressing the vector nature of momentum (or velocity) 1 point Scoring note: Responses do not have to correctly calculate the change in momentum. A response must show that the momentum (or speeds) have different directions, and that the difference in these two are the algebraic sum of the two magnitudes. Example response for part (b) ∆= p mv f − mvi KE = U g = ∆p ( 0.50 kg ) ( 4.7 1 mv 2 = mgh 5.1 Ns ∆p = i 2 = vi 2 gh = ( 2 10 U g = KE mgh = = vf 1 2 mv 2f 2 gh = ( 2 10 m s2 m) ) (1.5= 5.5 m) ) (1.1= 4.7 m s2 m s ) − ( 0.50 kg ) ( −5.5 m s m s m s Total for part (b) 3 points © 2022 College Board AP® Physics 1 2022 Scoring Guidelines (c) For attempting to calculate the area under the curve 1 point For comparing the area under the curve to the value of the change in momentum for part (b). 1 point For a correct justification that the impulse shown from the force sensor is not large enough to cause the ball to return to a height of 1.1 meters. 1 point Example response for part (c) The area under the force as a function of time graph is equal to the impulse or change in momentum of the ball. ∆pobserved = 5.1 Ns ∆= precorded 1 0.2 ( 2 ms )( 4 kN ) + ( 4 kN )( 0.6 ms ) + 12 ( 0.2 ms )( 4 kN ) ∆precorded = 3.2 Ns The change in momentum recorded by the force sensor is significantly smaller than the change in momentum determined from experimental data collected from the initial and final heights of the ball. It is likely that the force sensor reading cannot be trusted. Total for part (c) Total for question 5 3 points 7 points © 2022 College Board