Answer Happy

Activity 3: Once a Push Always a Push? Prediction P6. Consider the motion of the cart if you gave it a short push toward the detector and released it. In this scenario, there is a medium amount of friction. Sketch on the axes below your prediction for the velocity-time and acceleration-time graphs for this motion. Velocity (m/s) + 0 0 Acceleration (m/s²) 0 0 Time 5 (s) Time (s) 1) Tape the probe to the top of the cart as shown below and adjust the friction to medium friction. 2) Zero the force probe (with the string slack). Click on Collect. When you hear steady detector clicking, give the cart a short gentle push toward the motion detector by pushing on the force probe hook. Push so that the cart coasts to a stop between 10cm and 20cm from the detector. Be ready to catch the cart to keep it from hitting the detector. Hold the probe cord to the side of the cart and move the cord with the cart so that the cord tension does not tend to make the cart speed up or slow down. motion detector probe friction pad

3) Rescale the axes if necessary to see all of the graphs. Answer the following questions: a) At the instant the push ends, what does the force equal? b) At the instant the push ends, what does the acceleration equal? c) At the instant the push ends, what can you say about the speed of the cart? Look carefully at the graphs on the computer monitor Velocity (m/s) + 4) Use your answers in step 4 to sketch the velocity, force, and acceleration graphs on the axes below. Put numbers on the velocity and force axes. Force (N) + 0 0 0 0 Acceleration (m/s²) F = 0 a = Time (s) Time 5; (s) ¡Time (s) N m/s²

5) Show a vertical line on the 3 graphs above at the end of the push (the instant when the cart was released). Note: this line should cross all 3 graphs at the same time. Write 'End' above the line. It will be much easier to identify the time if you turn on the Analyze function by clicking on Analyze, Examine. This will give you a vertical line at the same time on all graphs. If the Analyze data box is in the way, click on the top bar of the box and drag the box to the right out of the way. 6) a) Is the velocity positive or negative for this run? b) Look at your acceleration graph (the red line on the bottom graph) and fill in a +,-, or a 0 in the sentences below. While the cart is speeding up its average acceleration is Watch the values in the acceleration graph box as you move the cursor from the end of the push to the end of the run at 5s. Complete the following sentence: While the cart is slowing down its average acceleration is What happens to the direction (sign) of the acceleration at the instant that the cart is released? On the diagram to the right, show an arrow for each force that is acting on the cart after you have released it. Question 6. What happened to the magnitude of the force of the push after you released the cart? Comment: When the net force acting on an object is zero, the velocity of the object does not change. The object either moves at a constant velocity or remains at rest. This law, which you have examined in this investigation, is known as Newton's First Law. V