2D kinematics? Have equations but making errors?

In summary, the minimum speed of the ball when it left the bat was approximately 36 m/s, when Babe Ruth hit a homerun over a 7.5-m-high right-field fence 95 m from home plate. This was calculated using the equation v = sqrt[(1 + 95 tan38 - (1/2)(9.8)(95)^2/(cos38)^2) / 7.5].
  • #1
pinkerpikachu
29
0
When Babe Ruth hit a homer over the 7.5-m-high right-field fence 95 m from home plate, roughly what was the minimum speed of the ball when it left the bat? Assume the ball was hit 1.0 m above the ground and its path initially made a 38º angle with the ground


2. Vx= Vcosθ x=horizontal distance, T=time, L=initial height h=final height
Vy= Vsinθ

x=vcosθT = x / vcosθ = T
h= L + vsinθT - (1/2)gT^2



The Attempt at a Solution



substituting for T

h= L + vsinθ(x / vcosθ) - (1/2)g(x / vcosθ)^2
h=L + xtanθ - (1/2)gx^2/ v^2 cosθ^2

v= sqrt[(L + xtanθ - (1/2)gx^2/cosθ^2) / h]

this should be how to get my answer which is 32, but I keep getting a number in the 90s. I actually get a negative under the sqaure root...but I ignore that...
 
Physics news on Phys.org
  • #2
For this particular problem, x=95 m, h=7.5 m, L=1 m, θ= 38º, g=9.8 m/s² Putting these into the equation yields: v = sqrt[(1 + 95 tan38 - (1/2)(9.8)(95)^2/(cos38)^2) / 7.5] This gives a value of 36 m/s.
 
  • #3


I would suggest double-checking your calculations and making sure you are using the correct units for each variable. It's possible that a small error in one of the equations or units could lead to a significantly different answer. Additionally, it may be helpful to review the equations and make sure you are using the correct one for the given scenario. If you are still having trouble, I would recommend seeking assistance from a classmate or instructor to help identify and correct any errors.
 

Related to 2D kinematics? Have equations but making errors?

What is 2D kinematics?

2D kinematics is the study of motion in two dimensions, typically represented by the x and y axes. It involves analyzing the position, velocity, and acceleration of an object in two-dimensional space.

What are the equations used in 2D kinematics?

The main equations used in 2D kinematics are the equations of motion, which include:

  • Position: x = x0 + v0t + 1/2at^2 and y = y0 + v0t + 1/2at^2
  • Velocity: v = v0 + at
  • Acceleration: a = (vf - v0)/t

Why am I making errors in my 2D kinematics calculations?

There could be a few reasons for making errors in 2D kinematics calculations:

  • Using incorrect equations or not understanding how to apply them correctly
  • Not accounting for vectors and their direction in the calculations
  • Not accurately measuring or recording data

How do I solve 2D kinematics problems?

To solve 2D kinematics problems, it is important to first understand the given information and identify what is being asked. Then, use the appropriate equations and plug in the given values to solve for the unknown variable. It may also be helpful to draw a diagram to visualize the problem and use vector components if necessary.

What are some real-life applications of 2D kinematics?

2D kinematics is used in many real-life scenarios, such as:

  • Calculating the trajectory of a projectile, such as a ball being thrown or a bullet being fired
  • Tracking the motion of objects in sports, such as a basketball player jumping or a tennis player hitting a ball
  • Analyzing the motion of vehicles in traffic or on a rollercoaster
  • Studying the movement of celestial objects, such as planets orbiting the sun

Similar threads

  • Introductory Physics Homework Help
Replies
2
Views
2K
  • Introductory Physics Homework Help
Replies
2
Views
3K
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
14
Views
10K
  • Introductory Physics Homework Help
Replies
2
Views
991
  • Introductory Physics Homework Help
Replies
5
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
22
Views
3K
  • Introductory Physics Homework Help
Replies
3
Views
698
Back
Top