Math Problem Statement

A projectile is thrown from the top of a 1.43 m high table at an angle 28 degrees and lands 5.48 m away horizontally. What is the init speed

Solution

To find the initial speed of the projectile, we need to apply the equations of projectile motion. The key idea is to break the motion into horizontal and vertical components.

Step 1: Break into components

Given dataTo find the initial speed of the projectile, we need to apply the equations of projectile motion. The key idea is to break the motion into horizontal and vertical components.

Step 1: Break into components

Given

  • Height of the table: h=1.43mh = 1.43 \, \text{m}
  • Angle of projection: θ=28\theta = 28^\circ
  • Horizontal distance (range): R=5.48mR = 5.48 \, \text{m}
  • Acceleration due to gravity: g=9.8m/s2g = 9.8 \, \text{m/s}^2

We need to determine the initial speed v0v_0.

Step 2: Horizontal motion equation

The horizontal distance covered is given by: R=v0cos(θ)tR = v_0 \cos(\theta) \cdot t where tt is the time of flight.

Step 3: Vertical motion equation

For vertical motion, the vertical displacement Δy=1.43m\Delta y = -1.43 \, \text{m} (since the projectile falls below its starting height) is given by: Δy=v0sin(θ)t12gt2\Delta y = v_0 \sin(\theta) \cdot t - \frac{1}{2} g t^2

Substitute Δy=1.43m\Delta y = -1.43 \, \text{m} and solve the system of equations to find the initial speed v0v_0.

Step 4: Solving for time tt

From the horizontal equation: t=Rv0cos(θ)t = \frac{R}{v_0 \cos(\theta)}

Substitute this into the vertical equation: 1.43=v0sin(θ)Rv0cos(θ)12g(Rv0cos(θ))2-1.43 = v_0 \sin(\theta) \cdot \frac{R}{v_0 \cos(\theta)} - \frac{1}{2} g \left( \frac{R}{v_0 \cos(\theta)} \right)^2

Now, solve this equation for v0v_0.

Let's compute this step-by-step.The positive solution for the initial speed v0v_0 is approximately 6.59m/s6.59 \, \text{m/s}.

Thus, the initial speed of the projectile is about 6.59 m/s.

Do you want more details or have any questions?

Here are 5 related questions for further practice:

  1. What would be the time of flight for the projectile?
  2. How would the initial speed change if the angle of projection were increased?
  3. What is the maximum height the projectile reaches during its flight?
  4. How does the range of the projectile change if the initial speed is doubled?
  5. What would happen to the range if the table height were halved?

Tip: In projectile motion, breaking the motion into horizontal and vertical components simplifies complex problems.

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Math Problem Analysis

Mathematical Concepts

Projectile Motion
Trigonometry
Kinematics

Formulas

Horizontal distance (range) formula: R = v_0 * cos(θ) * t
Vertical displacement formula: Δy = v_0 * sin(θ) * t - (1/2) * g * t^2
Time of flight: t = R / (v_0 * cos(θ))

Theorems

Equations of Motion under Constant Acceleration
Trigonometric Decomposition of Vectors

Suitable Grade Level

Grades 10-12