Velocity = displacement / time
First, Always make sure that your units for things are the same. In this question, we are given time in seconds and hours. So, we need to make them all use 1 unit.
I will do seconds.
To convert 80km/h to m/s, divide by 3.6.
22.2222…. m/s = displacement / 2.1s
Multiply by 2.1s on both sides
46.6666……m = displacement
You travelled 47 meters.
Answer:
24.6 - 11.2 / 4.4 = 3.045m/s
Explanation:
acceleration = vf-vi / time
vf= 24.6 m/s
vi= 11.2 m/s
t= 4.4s
Your question is missing one part as "magnification"
i have completed the missing part below
Answer:
a. 
b. 
Explanation:
For this type of numerical we will use the following formulas
......... Eq1
where,

refractive index of the medium surrounding refracting surface/object
i.e.
=

refractive index of the refracting surface/object
i.e. 
distance of object from the vertex of the refracting surface
distance of image from the vertex of the refracting surface
radius of curvature of the refracting surface
........... Eq2
where,
magnification
Convention:

Given:
=






because refraction surface is concave
Required:
a. 

b. 
Solution:
a. putting values in eq1, we get



cm
b. 
The weight changes but the mass will stay the same.
Assuming the cannonball is fired horizontally, its horizontal velocity stays at a constant 76 m/s. At the point it hits the ground, it has a speed of 89 m/s, so if its vertical velocity at that moment is
, we have

(taking the negative square root because we take the downward direction to be negative)
Recall that

where
and
are the initial and final velocities, respectively;
is the acceleration; and
is the change in position of a body. In the cannonball's case, it starts with 0 vertical velocity and is subject to a downward acceleration with magnitude
. So we have

(which is negative because we take the cannonball's starting position at the top of the cliff to be the origin) so the cliff is about 109 m high.