A ball is launched on a level surface toward a wall 80 meters away. If the launc

Question

A ball is launched on a level surface toward a wall 80 meters away. If the launch its way up is angle 36.87 degree and the initial speed is 50 m/s how high on the wall does the ball hit? Is it on its way up down at the time? What is the speed of the ball when it hits the wall? A box on a 30 degree incline is found not to be moving in the absence of all applied forces. What the smallest coefficient of friction (mu) that will permit this to happen? If a different box is accelerate down the same incline at 2 m/s^2 (again, in the absence of applied force) what is the value of mu consistent with that observation? What physical difference in the two situations account for the different values of mu?

Explanation / Answer

solving first question

Inital horizontal velocity=50cos(36.87)=40 m/s

time taken to travel 80 m =80/40=2 sec

initial vertical velocity=50sin(36.87)=30 m/s

height travelled in 2 sec

=30*2-0.5*9.8*4=40.4 m

maximum height is attained in time=50 sin(36.87)/9.8=3.06 sec

so it is up way as it is yet to achieve maximum height

vertival velocity after 2 sec =30-9.8*2=10.4 m/s

horizontal velocity=40 m/s

final velocity=sqrt(40*40 + 10.4*10.4)=41.3 m/s

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