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Grade 12Mechanics

A gun is mounted on a plateau 960 m away from its edge as shown. Height of a plateau is 960 m. The gun can fire shells with a velocity of 100 m/s at any angle. Of the following choices, what is the minimum distance (OP) x from the edge of a plateau where the shell of gun can reach ?

Question image for A gun is mounted on a plateau 960 m away from its
Profile image of S. Haris Ahmed Irfan
9 Years agoGrade 12
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Profile image of Askiitians Tutor Team
ApprovedApproved Tutor Answer1 Year ago

To determine the minimum distance (OP) from the edge of the plateau where the shell can land, we need to analyze the projectile motion of the shell fired from the gun. The key factors to consider are the height of the plateau, the initial velocity of the shell, and the angle at which it is fired.

Understanding Projectile Motion

Projectile motion can be broken down into two components: horizontal and vertical. The shell's initial velocity can be divided into these two components based on the angle of projection. The equations governing projectile motion will help us find the minimum distance from the edge of the plateau.

Key Variables

  • Height of the plateau (h): 960 m
  • Distance from the gun to the edge of the plateau: 960 m
  • Initial velocity (v): 100 m/s
  • Acceleration due to gravity (g): 9.81 m/s²

Calculating the Time of Flight

The time it takes for the shell to fall from the height of the plateau can be calculated using the formula for vertical motion:

h = (1/2) g t²

Rearranging this gives:

t = √(2h/g)

Substituting the values:

t = √(2 * 960 m / 9.81 m/s²) ≈ √(195.85) ≈ 14.0 seconds

Finding the Horizontal Distance

Now that we have the time of flight, we can calculate the horizontal distance the shell travels. The horizontal component of the initial velocity (v_x) depends on the angle of projection (θ):

v_x = v * cos(θ)

The horizontal distance (d) traveled during the time of flight is given by:

d = v_x * t = (v * cos(θ)) * t

Minimizing the Horizontal Distance

To find the minimum distance from the edge of the plateau, we need to consider the angle that minimizes the horizontal distance. This occurs when the shell is fired directly downward (θ = 90°), where:

v_x = 0

In this case, the shell will fall straight down, and the horizontal distance (OP) will simply be the distance from the gun to the edge of the plateau:

OP = 960 m

Conclusion

Thus, the minimum distance (OP) from the edge of the plateau where the shell can land is 960 m. This scenario illustrates how the angle of projection significantly influences the trajectory of a projectile, and in this case, firing straight down results in the minimum horizontal distance.