Answer:
Explanation:
Given
mass 
Force 
door knob is located at a distance of r=0.8 m from axis
Angular acceleration of door 
Torque 
where I=moment of inertia


Answer:
This is because normal force is exerted perpendicularly to the point of contact between the upper and lower objects.
Explanation:
This is because the upper object is still subject to gravitational pull. Therefore, the amount of force it exerts on the lower object due to gravity will be equal to the normal force that acts in the negative direction of gravitational force. Additionally, normal force is evident because the upper object will not go into the lower object.
Explanation:
Given that,
A ball is tossed straight up with an initial speed of 30 m/s
We need to find the height it will go and the time it takes in the air.
At its maximum height, its final speed, v = 0 and it will move under the action of gravity. Using equation of motion :
v = u +at
Here, a = -g
v = u -gt
i.e. u = gt

So, the time for upward motion is 3.06 seconds. It means that it will in air for 3.06×2 = 6.12 seconds
Let d is the maximum distance covered by it.

Putting all values

Hence, it will go to a height of 45.91 m and it will in the air for 6.12 seconds.
Distance for which the bike is ridden = 30 km
Speed at which the bike is driven = 0.75 km/minute
Let us assume the number of minutes taken to travel the distance of 30 km = x
Now we already know the formula of speed can be written as
Speed = Distance traveled/ Time taken
0.75 = 30/x
0.75x = 30
x = 30/0.75
= 40 minutes
So the time taken for riding a distance of 30 km will be 40 minutes. I hope this procedure is simple enough for you to understand.