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# Mechanics m1 edexel! watch

1. I'm stuck on two questions within the topic of kinematics of a particle any help would really be appreciated.
8. A Ball is thrown vertically upwards with a speed of 15 metres per second from a point 1m above the ground. Find the speed with which it hits the floor. If it rebounds with a speed which is half the speed with which it hits the floor, find its greatest height after the first bounce.
9. A particle is projected upwards with a speed of 14 meters per second. Find for how long it is above 2m.
2. 8) using SUVAT:
S= -1 since it is going to be moving down 1 meter
U= 15
A= -9.8
and we are trying to find V, the speed at which it hits the floor. using v^2=u^2+2as:
v^2=15^2+2(-9.8)(-1)
v^2=244.1
v=15.64 m/s

Then using SUVAT again the find it's greatest height on the second bounce
U = 7.82 half of the speed at which it hits the ground
A = -9.8
V = 0
and we are trying to find S, we can use v^2=u^2+2as
0=7.82^2+2(-9.8)(s)
0=61.15 - 19.6s
19.6s = 61.15
s = 3.12 m

9) First find the speed of the particle once it is 2m above the ground:
S = 2
U = 14
A = -9.8

V^2=U^2 + 2as
v^2 = 14^2 + 2(-9.8)(2)
v^2 = 156.8
v = 12.52m/s

Then find the time it takes to get from 2m to it's max. height
U = 12.52
V = 0
A = -9.8

V=U+AT
0=12.52-9.8t
9.8t=12,52
t=1.27s

since this is the time it takes to get from 2m to it's max height, multiply by 2 to get the total time above 2m

1.27 x 2 = 2.56s
3. (Original post by liam3781)
8) using SUVAT:
Giving full solutions isn't very helpful to the OP - you won't be there in the exam so in future try to give hints to allow them to work through it on their own, rather than just posting the answers
4. (Original post by fiimarie)
I'm stuck on two questions within the topic of kinematics of a particle any help would really be appreciated.
8. A Ball is thrown vertically upwards with a speed of 15 metres per second from a point 1m above the ground. Find the speed with which it hits the floor. If it rebounds with a speed which is half the speed with which it hits the floor, find its greatest height after the first bounce.
9. A particle is projected upwards with a speed of 14 meters per second. Find for how long it is above 2m.
As a general rule with Mechanics, always draw a diagram first with all of the information. It usually helps a lot and becomes clear what you need to do

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Updated: March 25, 2016
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