A 2.5-kg cannonball is red from the top of a cliff as shown in the figure below.

Question

A 2.5-kg cannonball is red from the top of a cliff as shown in the figure below. The cannonball leaves the
cannon at a height of h = 75 m above the ground below. The cannonball is fired at an initial speed of 120
m/s at an angle of = 30° above the horizontal. Use the coordinate system drawn on the figure for the
questions below.

1. Calculate the following quantities for the motion of the cannonball:

(a) What is the maximum height the object reaches?

(b) When does the object reach its maximum height?

(c) What is the minimum speed of the cannonball?

(d) When does the cannonball return to a height of 75 m after it has been red?

(e) When does the cannonball hit the ground?

(f) What is the speed of the cannonball just before it hits the ground?

Explanation / Answer

1a)

m= 2,5kg
g=9,81 m/s^2
h0= 75m
v0= 120m/s
v0y= sin(30)*120= 60m/s

Kinetic energy= (1/2)*m*v^2
Potential energy= mgh

Kinetic = Potential

(1/2)*2.5*60^2=2,5*9.81*h

h= 183,5m + 75m= 258.5m

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