2-D Kinematics and Projectile Motion

Mary Pruitt
physics 133 lab 1
STUDENT ID : 5773918

Pre-Lab Questions
1. In one of your experiments, you will roll a marble down a ramp to provide an initial horizontal velocity. Suppose you start the marble at rest (vo = 0 m/s) and it travels a distance of, d, down the ramp. Use 1-D kinematics to predict the velocity of the ball (vf ) at the bottom of the ramp. Hint: the acceleration of the ball down the ramp is 9.81*sin(?) m/s2 where ? is the angle of the ramp. Record you answer in variables (you will calculate the velocity with magnitudes when you perform the experiment).

= + 2*a*d

vo = 0 m/s, a = m/s2,

vf =

vf = 4.3*

2. Use the kinematic equations to derive a general equation for the time it takes a ball dropped from rest at vertical height, h, to reach the ground.

h = u*t + g*t2

For ball dropped from rest, u = 0 m/s

t =

3. Use the result from Question 2 to write a general equation for the distance travelled by a projectile that is rolling off a table of height, h, with a horizontal speed, v0x.

distance, d = speed*time

The distance travel d = vox*

Experiment 1: Distance Traveled by a Projectile
Data Sheet
Table 1. Range and Velocity of Projectile at Ramp Distance 1

Ramp Incline (degrees)

10

Ramp Distance (m):

000000

Trial

Measured Distance (m)

1

1.41

2

1.36

3

1.35

4

1.25

Average

1.35

Table 2. Range and Velocity of Projectile at Ramp Distance 2

Ramp Distance (m):

111

Trial

Measured Distance (m)

1

1.61

2

1.55

3

1.50

4

1.58

Average

1.58

Table 3. Range and Velocity of Projectile at Ramp Distance 3

Ramp Distance (m): 0.9

001.2

Trial

Measured Distance (m)

1

1.52

2

1.58

3

1.53

4

1.61

Average

1.56

Post-Lab Questions
1. Use your predictions of velocity and range from the Pre-Lab Questions and the data recorded from your experiment to complete Table 4.

Table 4. Velocity and Range Data for all Ramp Distances

Ramp Distance (m)

Calculated

velocity (m/s)

Predicted Range (m)

Average Actual Range (m)

Percent Error

2. How do your predictions compare to the observed data? Explain at least two reasons for the differences.

3. If you were to fire a paintball pellet horizontally and at the same time drop the same type of paintball pellet you fired from the paintball gun, which pellet would hit the ground first and why is this so?

if there was no resistance, the vertical velocities of both pellets would grow at the same rate and they both would hit the ground at the same time. The resistance grows with speeds, so the pellet would hit the ground first. The dropped pellet will hit the ground first (assuming the ground is perfectly horizontal and smooth, as the difference between the pellets would normally be very small). Resistance sometimes act as a barrier to the motion of falling objects.

4. Suppose you altered your existing ramp so that the marbles had twice their initial velocity right before leaving the ramp. How would this change the total distance traveled and the time that the marbles were in the air?

They would hve gained more speed allowing for further distance. However, for the falling part it will be the same because gravity will still put on the marble at the same rate. The speed will allow for further distance not further time.

5. Describe the acceleration of the marble after it leaves the ramp. Use kinematic equations to support your discussion.

When the marble officially leaves the ramp, the velocity vs the initial velocity will change as the replacement of the marble increases the further the marble gets from the rmap.

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