Question Q1. Look at the force graph for the time interval when the speed was increasing steadily. If you smoothed out the bumps and dips, would you describe the force as increasing, constant, or decreasing? Q2. Is this what you expected? If not, how does the force graph differ from your prediction? Lab 3: V vs T Lab 4: Vectors Lab 5: Newton's Laws 1 Lab 6: Newton's Laws 2
Velocity (m/s) Force (N) Acceleration (m/s) + 0 Time 5(s) Time si Time 51(s) Force + Force + 0 Force + 0- Force + Force + 0- Time Time Time Time Time
Q3. Look at the acceleration graph for the time interval when the speed was increasing steadily. If you smoothed out the bumps and dips, would you describe the acceleration as increasing, constant, or decreasing? Q4. Is this what you expected? If not, how does the acceleration graph differ from your prediction? Activity 2: Accelerating a More Massive Cart In this activity you will examine what force is needed to accelerate a heavier cart with the same acceleration as in Activity 1. Prediction P2. If you pull a heavier cart so that its velocity-time graph is identical to the velocity-time graph for the lighter cart, a) How will the force graph for the heavier cart differ from the force graph for the lighter cart? b) How will the acceleration graph for the heavier cart differ from the acceleration graph for the lighter cart?
Test your predictions as follows: 1. Determine the mass of the cart using the triple beam balance. Cart Mass= 0.235 kg 2. New mass of the cart = cart mass + added mass= 0.285 kg 3. Place the cart at the 10cm mark on the track. Lay the probe on the track and zero the probe (in the horizontal position with the string slack). 4. Click on Collect. Pull the cart so that its velocity-time graph matches your Run #1 velocity graph. Repeat as many times as necessary to get a good match. 5. Save your graph as Run #2 by clicking on Experiment, Store Latest Run. 6. Sketch these graphs using dashed lines on the same axes used above for the lighter cart. Label the lines as "heavier cart". Question Q5. Did your force and acceleration graphs agree with your predictions? Describe any differences below. Review Questions 1-5 refer to an object free to move along the x axis (horizontally) for which friction is negligible. Sketch the graph of the applied force vs time needed to produce the motion described. 1. The object moves to the right (the +x direction) with constant velocity.
2. The object moves to the right with steadily increasing velocity (a constant acceleration). 3. The object moves to the right first with increasing speed and then with decreasing speed. 4. The object moves to the left (the -x direction) with a steadily increasing velocity. 5. The object moves to the left first with increasing speed and then with decreasing speed. 6. The velocity vs. time graph for an object moving in a straight line is hown on the right. Sketch using solid line () the shapes of the acceleration and net force graphs on the axes to the right for this object. Velocity 0 Acceleration 0 0 Net Force 0 Acceleration 0 0 Net Force 0 R-2 3 5 Time Time 5 (s) Time (s) Time (s) Time (s)
7. An object moves with the acceleration shown to the right. Sketch on the bottom axis the graph of the net force on the object.
Investigation B: Motion with Constant Acceleration Purpose: To find out how to produce motion with constant acceleration and to find the relationship between force and acceleration. Materials: Vernier LabPro, two slotted cart masses, force probe, motion detector, 100G masses and other assorted masses, cart, smooth track Activity 1: Pulling a Cart to Make It Speed Up Steadily Prediction P1. Consider a cart (with friction) that is moving away from the detector with a steadily increasing speed. Sketch on the axes on the next page the velocity, acceleration, and applied force graphs you would expect if you pulled on the cart to produce this motion. Label each line as "prediction". 1. Computer Setup: Open Logger Pro program and verify Force and Velocity graphs. 2. Remove the tape and verify that the cart has medium friction. 3. Remove the force probe from the cart and lay it on the ramp in a horizontal position. Attach a string to the cart and force probe like you did in activity 1. Be sure the string is slack and zero the force probe. 4. Place the cart 10 cm from the detector. Click on Collect. Wait 1 second before you start pulling, then make the velocity increase steadily to a maximum final speed of 0.4m/s. Repeat as many times as necessary to get the straightest line possible on you velocity graph. Be careful to keep the probe handle parallel to the track at all times. 5. Adjust the limits of your axes if necessary to see all of your data. Then sketch your actual force, velocity, and acceleration graphs on the axes on the following page. When doing a sketch, leave out the smaller bumps and dips on the graph. 6. Save your graph as Run #1 by clicking on Experiment, Store Latest Run. Investigation B: Motion with Constant Acceleration Purpose: To find out how to produce motion with constant acceleration
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