Please, can someone help me with Physics
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Please, can someone help me with Physics

[From: ] [author: ] [Date: 11-12-15] [Hit: ]
81 * 0.5 = 4.the velocity after 0.= sq root [ 4.......
I have tried these two questions a few times, and I can't figure out how to do them!

1) A ball is kicked off the side of a cliff that is 40 meters high with an initial velocity of 20 m/s. How long does it take to reach the ground? AND What is the velocity after 0.5 seconds?

2) A crate is accelerated from rest to a velocity of 10 m/s in 5 seconds with a force of 40N. What is the mass of the object?

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2) u=0; v=10; t=5
v=u+at
10 = 0 + 5a
a =2
force = mass * a
40 = m * 2
m = 20 kg
answer

1) assuming ball was kicked horizontally
vertical motion
s= ut + 0.5 at^2
40 = 0 + 0.5 * 9.81 * t^2
t = 2.856s
time it take to reach the ground
answer

v = u + gt
v = 0 + 9.81 * 0.5 = 4.905
vertical speed component
the velocity after 0.5 seconds
= sq root [ 4.905^2 + 20^2]
m/s
answer
1
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