[cloud47]

A place kicker must kick a football from a point 36.0 m from the goal, and the ball must clear the crossbar, which is 3.05 m high. When kicked, the ball leaves the ground with a speed of 20.0m/s at an angle of 53 to the horizontal.
a) By how much does the ball clear or fall short of clearing the crossbar?
b)Does the ball approach the crossbar while still rising or while falling?

Please help me!

[Chery]

If this is a question for a school project, then please place your theory here for people to review and to give you hints, this will make it better for your self-esteem to do the project yourself. Good luck, and welcome to the forum.

[karttikeya]

I got answer it is 1.43 metres and falling
first horizontal component of the velocity =20xcos(53)=12.03 m/s
so time taken to cover 36m is= 36/horizontal velocity=approx 3 seconds

now vertical component of the velocity is = 20xsin (53)=15.97 m/

now time taken to reach the highest point is 15.97/9.8 = 1.68 seconds

so time left for ball to fall is 1.32 seconds

total distance covered by ball vertically in that period is s=(1/2)(9.8)(1.32)(1.32) = 8.53 metres from the top point

max height reached is (15.97)(15.97)/(2)(9.8)= 13.01 metres

thus after 3 seconds it will be 13.01-8.53=4.48 metres above ground

which is higher than 3.05 metres so it will clear the ar by 1.43 metres approx. and it will be falling

[karttikeya]

Hope it helps

[Unknown008]

Unfortunately, I don't think that it helps since the question was asked 5 years ago.

Also, you have a mistake in your solution.

When you take the vertical component of the velocity, you need to consider gravity also, meaning that:



Then, for 3 seconds, you get the height reached as 3.82 m, which means the ball clears the crossbar by 0.77 m.

Then you get 1.62 s as the time to reach the highest point, which means that the ball is falling when it clears the crossbar.

[samanta08]

Can you make it step by step!!