Projectile Motion Ball off Cliff Help

AI Thread Summary
To solve the projectile motion problem, the initial horizontal velocity (v_0x) is calculated as 22 m/s using the formula x = v_0x * t. The vertical motion equation must incorporate the cliff height, leading to the correct equation y = (v_0y)t + 0.5gt^2, where g is the acceleration due to gravity. The vertical component of the initial velocity (v_0y) is found to be approximately 40.905 m/s, but the calculations need to ensure the cliff height of 46 m is properly included. The discrepancy with the instructor's answer suggests a miscalculation or oversight in applying the kinematic equations. Accurate application of both horizontal and vertical motion equations is essential for determining the initial velocity and launch angle.
caels
Messages
5
Reaction score
0
I missed a few days of class and have a quiz tomorrow so I'm not entirely sure where to start with this. The question is:

A golfer hits a ball (m = 38 g) from a cliff top (h = 46 m) and times how long it takes to splash in the ocean (t = 7.0 s). The ball hits the water at a distance (x = 154 m) from the vertical cliff bottom. Find the ball's initial velocity and the angle of launch.

I have y = 46 m, x = 154 m, t = 7.0 s

I assume I have to use the two-dimensional kinematic equations, but I just can't seem to get anywhere towards finding the initial velocity.

My first thought was

x = v_0x * t

v_0x = 154 / 7 = 22 m/s

Then take

y = (v_0y)t+1/2 gt^2 = 7(v_0y) - 240.34

v_0y = 40.905

And then square both of those and take the square root. But the answer I get doesn't agree with the instructors, so I'm lost.
 
Physics news on Phys.org
You did not use the cliff height in the second equation.
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top