Answer:

3m/s

Explanation:

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Given that the balloon starts with an acceleration of 4 m/s² and its acceleration is linearly decreasing with height, we can assume the relationship between acceleration and height to be:

a = k * h

Where:

- a is the acceleration

- h is the height above the ground

- k is a constant

We are given that the acceleration becomes zero at a height of 3 m, so we can find the value of k:

0 = k * 3

k = 0

This implies that the acceleration is directly proportional to the height, but since k is zero, it means the acceleration remains constant at zero once it reaches a height of 3 m.

Now, let's consider the motion of the balloon from the ground up to a height of 3 m. Since the acceleration is zero during this interval, the balloon is moving with a constant velocity.

Next, from a height of 3 m to a height of 1.5 m, the balloon will continue to move with the velocity it attained at 3 m. This is because there are no forces acting to change its velocity, as the acceleration is zero.

Therefore, the speed of the balloon at a height of 1.5 m is the same as the velocity it attained at a height of 3 m. Since the initial velocity is zero and there is no change in velocity due to zero acceleration, the speed at 1.5 m is also zero.

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