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A ball is thrown from a point A at a target T, which is on horizontal ground - Leaving Cert Applied Maths - Question 3 - 2016

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A ball is thrown from a point A at a target T, which is on horizontal ground. The point A is 17.4 m vertically above the point O on the ground. The ball is thrown fr... show full transcript

Worked Solution & Example Answer:A ball is thrown from a point A at a target T, which is on horizontal ground - Leaving Cert Applied Maths - Question 3 - 2016

Step 1

(i) the time taken for the ball to travel from A to B

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Answer

To find the time taken for the ball to travel from point A to B, we can use the vertical motion formula. The vertical displacement is given by:

y=v0yt+12gt2y = v_{0y}t + \frac{1}{2}gt^2

where:

  • v0y=25sin(30°)v_{0y} = 25 \sin(30°) (initial vertical speed)
  • g=9.81 m/s2g = 9.81 \text{ m/s}^2 (acceleration due to gravity)
  • The displacement yy is -17.4 m (since it moves downward).

Setting up the equation:

17.4=12.5t4.905t2-17.4 = 12.5t - 4.905t^2

This can be rearranged into a quadratic equation and solved using the quadratic formula to find the value of t.

Step 2

(ii) the distance TB

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Answer

To find the horizontal distance from point A to point B, we first need the horizontal component of the initial velocity:

v0x=25cos(30°)v_{0x} = 25 \cos(30°)

Using the time calculated from part (i):

x=v0xtx = v_{0x} t

where tt is the time taken calculated in part (i). Thus,

TB=(25cos(30°))t.TB = \left( 25 \cos(30°) \right) t.

This needs to be calculated using the total time.

Step 3

(iii) Find the speed of the ball at C

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Answer

The speed of the ball at point C can be found by considering the components of the velocity.

  1. The vertical component of the velocity at point C is: vy=v0y+gtv_y = v_{0y} + gt
  2. The horizontal component remains the same: vx=v0xv_x = v_{0x}
  3. The total speed at point C can be calculated using: v=vx2+vy2|v| = \sqrt{v_x^2 + v_y^2} Plugging in the values calculated from the previous parts to find the exact speed.

Step 4

(b) Find the value of k correct to one decimal place

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Answer

Using the formula for the maximum range:

R=ku2gR = \frac{ku^2}{g}

We also know that the angle of projection θ\theta and the inclined plane will affect this range. To find kk, we need to derive the formula based on the motion equations and substitute the known values to isolate kk for final calculation.

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