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vivekrai
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Homework Statement
http://u.spig.in/forum/105599049.jpg
A projectile is fired at t=0 with velocity v = 20√2 m/s at an angle of 45° degrees as shown. A wall inclined at the same angle and at a distance of 40 m starts moving towards the projectile at the same time (ie., t=0) with a speed of 20m/s. Find the time at which the ball collides with the the wall.
Homework Equations
General Kinematical Equations
The Attempt at a Solution
I'm getting answer as 2(√3-1) s. Strikingly this is very similar to my friend's answer i.e, 2(√2-1) s. I don't know whose one is correct. Help me.
My Solution,
Let the base of the wall has moved a distance 40-x m at the time the ball collides with the wall. Let the height at which the collision occurs is y.
Then we have,
20t = 40-x ... (1) (for wall)
y = 20t-5t2 ... (2) (for ball)
and x+y=20t ... (3) (General diagram and since angle is 45 deg)
Solving for ' t ' , a quadratic I got, t = 2(√3-1) s (Other value being negative)
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