Answer:False.
Explanation: HIV is a viruse that only shows symptoms after a few weeks. in Fact HIV does not show any physical symptoms. So, no you can not tell if someone has or is been infected by HIV by directly looking at them.
Have a Nice Day!!! =)
Answer:
c) The pitch of the two sirens sounds the same to you
Explanation:
The pitch does not depend on the distance of the object from the observer.
As per the given data
pitch = frequency
Frequency =

=

Hence, the pitch of the two sirens remains the same for the observer.
When object reached the terminal speed then its acceleration is zero
So as per Newton's II law we can say

now in that case we can say that net force is zero so here weight of the object is counter balanced by the drag force when it will reach at terminal speed
so we can write

so here we are given that





so terminal speed will be nearly 2 m/s
Answer:
Explanation:
mass of first marble 
Initial velocity of the first marble
considering right side as positive
Mass of second marble
After collision first marble moves to the left with a velocity of 18 cm/s
i.e. 
considering
be the velocity of second marble after collision
The Coefficient of restitution is 1 for an elastic collision

Putting values

So, the velocity of the second marble is 22.5 m/s to the right after the collision
(b)Initial kinetic energy =
Final kinetic energy=

Answer:
The bird's speed immediately after swallowing is 4.98 m/s.
Explanation:
Given that,
Mass of bird = 290 g
Speed = 6.2 m/s
Mass of sees = 9.0 g
Speed = 34 m/s
We need to calculate the bird's speed immediately after swallowing
Using conservation of momentum

Put the value into the formula



Hence, The bird's speed immediately after swallowing is 4.98 m/s.