Answer:
Higher frequency.
Explanation:
Sound are mechanical waves that are highly dependent on matter for their propagation and transmission.
Sound travels faster through solids than it does through either liquids or gases. A student could verify this statement by measuring the time required for sound to travel a set distance through a solid, a liquid, and a gas.
Mathematically, the speed of a sound is given by the formula:
Generally, the frequency of a sound wave determines the pitch of the sound that would be heard.
A shrill sound refers to a type of sound that is typically sharp, high pitched and as such has higher frequency.
Hence, shrill sound is of higher frequency.
Answer:
Explanation:
Given
mass of bus along with travelers travelling in North direction is 
speed of bus towards North 
mass of bus travelling in South direction is 
speed of bus 
mass of each Passenger in south moving bus 
Momentum of North moving bus



Momentum with south moving bus


For total momentum to be towards south
should be greater than 0
thus for least value of n



Answer:
the angle of incident is 40°
Explanation:
NQ is the normal to the mirror, therefore
angle NQA =90°
PQA = 50°
incident angle = NQA - PQA
90°- 50° = 40°
note that the angle of reflection is equal to the angle of incident
The aluminum atom_loses_____electrons to form an ion.
The ion that is formed is_Al³⁺_____.
aluminium has the electronic configuration as 1s² 2s² 2p⁶ 3s² 3p¹
from the electronic configuration , we see that aluminium can attain stability by losing 3 electrons from outer shell.
after losing 3 electrons , the ion formed is given as Al³⁺
hence the correct options to fill in the blanks are lose and Al³⁺