Math Problem Statement

The maximum horizontal distance a boy can throw a ball is 52 m. Assume he can throw with the same initial speed at all angles. How high does he throw the ball when he throws it straight upward?

Solution

To solve this problem, we need to relate the maximum horizontal distance the ball can be thrown to the maximum height it reaches when thrown vertically.

Given Information:

  • Maximum horizontal distance (RR) = 52 m
  • Initial speed (v0v_0) is the same for both horizontal and vertical throws.

Horizontal Throw Analysis:

The maximum range RR for projectile motion is given by the formula:

R=v02sin2θgR = \frac{v_0^2 \sin 2\theta}{g}

where:

  • v0v_0 is the initial speed,
  • θ\theta is the angle of projection,
  • gg is the acceleration due to gravity (approximately 9.8m/s29.8 \, \text{m/s}^2).

For maximum range, θ=45\theta = 45^\circ. So, sin2θ=sin90=1\sin 2\theta = \sin 90^\circ = 1.

Thus, the equation simplifies to:

R=v02gR = \frac{v_0^2}{g}

Plugging in the values, we get:

52=v029.852 = \frac{v_0^2}{9.8}

Solving for v0v_0:

v02=52×9.8=509.6m2/s2v_0^2 = 52 \times 9.8 = 509.6 \, \text{m}^2/\text{s}^2 v0=509.622.57m/sv_0 = \sqrt{509.6} \approx 22.57 \, \text{m/s}

Vertical Throw Analysis:

When the ball is thrown straight up, the maximum height (HH) it reaches is given by:

H=v022gH = \frac{v_0^2}{2g}

Substitute the value of v02=509.6v_0^2 = 509.6:

H=509.62×9.8H = \frac{509.6}{2 \times 9.8} H=509.619.626mH = \frac{509.6}{19.6} \approx 26 \, \text{m}

Thus, the maximum height the boy can throw the ball vertically upward is approximately 26 meters.

Would you like more details or have any questions? Here are some related questions you might find interesting:

  1. How would the maximum height change if the acceleration due to gravity were different?
  2. What would the maximum range be on the Moon, where gravity is 1/6th of Earth's gravity?
  3. How long does the ball stay in the air when thrown vertically?
  4. How much time does the ball take to reach its maximum height when thrown vertically?
  5. What is the speed of the ball at its highest point when thrown vertically?

Tip: The angle of 4545^\circ is ideal for achieving the maximum range in projectile motion, assuming no air resistance.

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Math Problem Analysis

Mathematical Concepts

Projectile Motion
Kinematics
Energy Conservation

Formulas

Range formula: R = (v_0^2 * sin 2θ) / g
Maximum height formula: H = v_0^2 / (2g)
Relationship between initial speed and range: R = v_0^2 / g

Theorems

Projectile Motion Formula for Maximum Range
Energy Conservation in Vertical Motion

Suitable Grade Level

Grades 9-12