Given information:
- Initial velocity (u) = 30 m/s towards East
- Final velocity (v) = 40 m/s towards North
- Time interval (t) = 10 s

Step 1: Calculate the change in velocity (Δv)
The change in velocity is given by the difference between the final velocity and the initial velocity.
Δv = v - u

In this case, the final velocity is towards North and the initial velocity is towards East. These velocities are perpendicular to each other, so we can use the Pythagorean theorem to find the magnitude of the change in velocity.
Δv = sqrt(v^2 + u^2)

Substituting the given values,
Δv = sqrt((40)^2 + (30)^2)
Δv = sqrt(1600 + 900)
Δv = sqrt(2500)
Δv = 50 m/s

Step 2: Calculate the average acceleration (a)
The average acceleration can be calculated using the formula:
a = Δv / t

Substituting the values,
a = 50 m/s / 10 s
a = 5 m/s²

Step 3: Interpretation
The average acceleration of the body is 5 m/s². This means that for every second, the body's velocity changes by 5 m/s in the direction of the change. In this case, the body's velocity changed from 30 m/s towards East to 40 m/s towards North in a time interval of 10 seconds. The acceleration indicates how quickly the velocity changed during this time interval.

Conclusion
The average acceleration of the body is 5 m/s². This value represents the rate of change of velocity over a given time interval.

A= 3i + 4 j .. |a|= 5 m/sec2