Any three differences between acceleration and retardation are:

Solution:

Initial velocity of car (u) = 45 km/hr = 45 * 1000/3600 = 12.5 m/s

Time taken (t) = 3 s

Since the car stops finally, final velocity of car (v) = 0 m/s

Now,

Retardation (-a) = (u - v)/t

= (12.5 - 0)/3

= 4.17 m/s²

Hence, the magnitude of retardation of the car is 4.17 m/s².

Let the car move a distance 's' before coming into rest than from equations of motion, we have,

s = ut - 1/2 (a)t² [acceleration is negative due to retardation]

= (12.5)3 - 1/2 (4.17) (3)²

= 18.375 m

Hence, the car travelled...

Given

initial velocity ( u ) = 72 km/hr = 72 x 1000 / 3600

= 20 m/s

acceleration due to gravity (g) = 10 m/s²

also, final velocity(v) = 0 m/s

for maximum height,

v² = u² - 2gH

or, 0 = 20² - 2 x 20 H

thus, H = 400/ 40

maximum height (H) = 10 m

again , for time to return to initial position.

total displacement(s) = 0

so,

s= ut - 1/2 gt²

or, ut = gt²

thus, T = u/g

= 20/10

total time taken = 2 sec

The fan tends to continue its circular motion even after it is switched off due to the inertia of motion. The fan rotates with a decrease in speed (this is because of air friction) and stops after a few minutes.

Forces are said to be balanced when there is no net push or pull acting on the body experiencing the force. Example: balanced condition of tug of war, etc.

Forces are said to be unbalanced when there is some push or pull acting on the body experiencing the force. Example: when a team pulls another team in a tug of war, etc.

Solution:

Initial velocity of stone (u) = 72 km/hr = 72 * 1000/3600 = 20 m/s

The stone is acted by constant downward acceleration equal to the acceleration due to gravity of earth, i.e, a = -g = - 10 m/s²

At maximum height, the velocity of the stone becomes 0 for a very short time so, final velocity of stone (v) = 0 m/s

To find: maximum height (H) = ?

Using equations of motion,

v² = u² + 2aH

or, 0² = (20)² + 2(-10)H

or, 0 = 400 - 20H

or, 20H = 400

or, H = 400/20

So, H = 20 m

Hence, the maximum height...

Velocity is the rate of change of displacement.

Mathematically, Velocity (V) = displacement / time

If car A travels 10 meters in 5 seconds in a straight line, it's velocity is 2 m/s.