Answer:
Few millimeter thick aluminium, water, wood, acrylic glass or plastic.
Explanation:
The materials that are best for protection against beta particles are few millimeter thickness of aluminium, but for the high energy beta-particles radiations the low atomic mass materials such as plastic, wood, water and acrylic glass can be used.
These materials can also be used in personal protective equipment which includes all the clothing that can be worn to prevent any injury or illness due to the exposure to radiation.
Answer:
27.5 m/s
Explanation:
applying motion equations we can find the answer,
v = u + a*t
Let assume ,
u = starting speed(velocity)
v = Final speed (velocity)
t = time taken for the motion
a = acceleration
by the time of reaching the highest point subjected to the gravity , the speed should be equal to zero (only a vertical speed component is there)
for the complete motion it takes 5.5 s. that means to reach the highest point it will take 5.5/2 =2.75 seconds
we consider the motion upwards , in this case the gravitational acceleration should be negative in upwards (assume g=10 m/s2)
that is,
v = 0 , a = -10
, t =2.75
v = u + at
0 = u -10*2.75
u = 27.5 
The height above the ground from where the skier start is 11.5 m.
<h3>
Conservation of energy</h3>
The height above the ground from where the skier start is determined by applying the principle of conservation of energy as shown below;
P.E = K.E
mgh = ¹/₂mv²
gh = ¹/₂v²

Thus, the height above the ground from where the skier start is 11.5 m.
Learn more about conservation of energy here: brainly.com/question/166559