Answer:
The time take is 
Explanation:
From the question we are told that
The decay constant is
The percentage fall is 
The equation for radioactive decay is mathematically represented as

Where is
is the new amount of the new the isotope while
is the original
At initial
% = 1
At
% = 0.80

=> 
=> 
0.67s
Explanation:
Given parameters:
Speed of bullet = 600m/s
Distance of target = 400m
Unknown:
Time taken for bullet to reach target = ?
Solution:
Speed is a physical quantity that expresses the rate of change of distance with time;
Speed = 
Since time is unknown, we make it the subject of the expression;
time =
= 
time = 0.67s
Learn more:
Speed brainly.com/question/10048445
#learnwithBrainly
Answer:
A 10 N force pointing up
Explanation:
If the net acceleration of the object is horizontal pointing to the right, that means that all vertical forces must have canceled out, and the only ones "unbalanced" are the horizontal ones (10 N to the right minus 5 N to the left giving a net force of 5 N to the right).
Since they mentioned only one vertical force pointing down (10 N), there must be another one of same magnitude but pointing in opposite direction (up).
Then there must also be a 10 N force pointing up acting on the object.
Answer:
uh finish the question please lol.
Answer:

Explanation:
Here two charges are placed at distance "d" apart
now the net value of electric field at some position between two charges will be ZERO
so we will have
electric field due to charge 1 = electric field due to charge 2

Let the position where net field is zero will lie at distance "r" from q1

now we will have

now square root both sides

now we have

so we have
