Lab 3 Acceleration Due to Gravity!

Objective The purpose of the lab is to measure the acceleration due to gravity during free fall and to observe cases when free fall does not apply.

Equipment Motion sensor, rubber ball, wooden board.

The Acceleration Due to Gravity The acceleration due to gravity at the surface of the Earth is constant. It has a magnitude of 9.807 m/s2. It is in the downward direction. According to Newton’s second law of motion, when an object is affected by Earth’s gravity only, it will accelerate at the rate. This is called free fall. An object that does not have this acceleration must have other forces acting on it.

Experiment 1: Bouncing Ball Place the motion sensor’s face about 1 m from the table or the floor facing down. See the picture on the right. Set it to record at 50 Hz.

Drop the ball from a height about 10 cm below the motion sensor. Attempt to acquire the following position as a function of time data. In order to do this, minimize the rotation of the ball or put the right amount of spin on it to keep it directly under the sensor. Record three bounces of the ball which will contain two airborne sections as well. See the sample diagram.

position

time

page 1 When interpreting the data, remember that the motion sensor measures the distance of the object in front of it. Also, the direction pointing away from the motion sensor is the positive direction. We will look at the data in the regions shown below.

bounce 1 bounce 2 bounce 3 position

time leg 1 leg 2 leg 3 leg 4

To find the acceleration, display the velocity vs time graph. Identify the regions in the velocity graph that correspond to the regions above. For each region, determine the slope of the velocity graph. This is the acceleration. Include the uncertainty of the dlope. Make a table of the regions above.

acceleration net force probability of regions free fall? (Y/N) (m/s2) direction agreement bounce 1 leg 1 leg 2 bounce 2 leg 3 leg 4 bounce 3

For the acceleration, indicate the magnitude and the (real-life, up or down) direction. Indicate the direction of the net force on the ball. Indicate, also, the probability of agreement between the experimental acceleration and the expected acceleration for free fall. Calculate this as the probability that the result will fall within 5% of 9.8 m/s2. Since the data was taken by a machine, the 5% tolerance is larger than necessary, but it’ll show us just how good it is.

Question 1 In which regions do the data indicate that the acceleration is likely completely due to gravity so that we can conclude that it is in free fall?

page 2 Experiment 2: Falling Board Repeat the above experiment with a falling wooden board. Drop it on a piece of foam. Of course it will not bounce so there is only one leg.

acceleration net force probability of regions free fall? (Y/N) (m/s2) direction agreement leg 1

Question 2 Does the data indicate that the acceleration is likely completely due to gravity so that we can conclude that it is in free fall?

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