Answer:
a) 
b) 
Explanation:
Given:
mass of ball, 
initial speed of the ball, 
mass of the person, 
a)
Using the conservation of linear momentum:
When the person catches the ball, assuming that the person catches it with an impact without absorbing the shock.



b)
When the ball hits the person and bounces off with the velocity of
.
Using the conservation of linear momentum:

where:
final speed of the ball after collision
final speed of the person after collision
initial velocity of the person = 0
putting the respective values in the above eq.


the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes.
Step by step solution :
standard deviation is given by :

where,
is standard deviation
is mean of given data
n is number of observations
From the above data, 
Now, if
, then 
If
, then 
if
, then 
If
, then 
If
, then 
so, 



No, Joe's value does not agree with the accepted value of 25.9 seconds. This shows a lots of errors.
Answer:
d = 52 μm
Explanation:
given,
wavelength of the light source (λ)= 550 nm
distance to form interference pattern(D) = 1.5 m
y = 1.6 cm = 0.016 m
width of the slits = ?
now, using displacement formula
for the first maxima, m = 1
d = 5.2 x 10⁻⁶ m
d = 52 μm
hence, the width of her slits is equal to d = 52 μm