a small brick mass 700 g is projected vertically downwards at a velocity of 1,25(m/s) from the top of a building of height 25m.calculate the magnitude of the velocity at which the brick hits the ground?

we need

25-1.25t-4.9t^2 = 0
t=2.135

so, we have a final v of

v = -1.25 - 9.8(2.135) = ?

To calculate the magnitude of the velocity at which the brick hits the ground, we can use the principles of kinematics.

1. Start by determining the initial velocity of the brick (v₀). Since the brick is projected downwards, the initial velocity has a negative value. So, v₀ = -1.25 m/s.

2. Next, determine the acceleration of the brick (a). In this case, the brick is moving in the vertical direction under the influence of gravity. Therefore, the acceleration is given by the gravitational acceleration, which is approximately 9.8 m/s².

3. Now, we can use the following equation of motion to find the final velocity (v) when the brick hits the ground:
v² = v₀² + 2aΔy

Where:
v = final velocity
v₀ = initial velocity
a = acceleration (gravity)
Δy = change in height (25 m, since the brick fell from the top of a 25 m building)

4. Substitute the given values into the equation:
v² = (-1.25 m/s)² + 2(9.8 m/s²)(-25 m)

5. Calculate the equation:
v² = 1.5625 m²/s² + (-490 m²/s²)

v² = -488.4375 m²/s²

6. Take the square root of both sides of the equation to find the magnitude of the velocity:
v = √(-488.4375 m²/s²)
v ≈ 22.1 m/s

So, the magnitude of the velocity at which the brick hits the ground is approximately 22.1 m/s.

To calculate the magnitude of the velocity at which the brick hits the ground, we can use the principles of kinematics and the equations of motion.

First, let's define our variables:
- Initial velocity (u) = 1.25 m/s (velocity at the top of the building)
- Final velocity (v) = ? (velocity when the brick hits the ground)
- Time (t) = ? (time taken for the brick to fall)
- Height (h) = 25 m (height of the building)
- Acceleration due to gravity (g) = 9.8 m/s^2 (assuming downward direction)

Now, we can start solving the problem step by step:

Step 1: Calculate the time taken for the brick to fall.
We can use the equation of motion: h = ut + (1/2)gt^2, where h is the height, u is the initial velocity, g is the acceleration due to gravity, and t is the time.

Plugging in the values, we get:
25 = (1.25)t + (1/2)(9.8)(t^2)

Simplifying and rearranging the equation, we get a quadratic equation:
4.9t^2 + 1.25t - 25 = 0

Solving this quadratic equation, we find that t can be approximately 2.418 seconds (rounded to three decimal places).

Step 2: Calculate the final velocity when the brick hits the ground.
We can use the equation of motion: v = u + gt, where v is the final velocity, u is the initial velocity, g is the acceleration due to gravity, and t is the time.

Plugging in the values, we get:
v = 1.25 + (9.8)(2.418)

Simplifying the equation, we find that the final velocity (v) is approximately 24.38 m/s (rounded to two decimal places).

Therefore, the magnitude of the velocity at which the brick hits the ground is approximately 24.38 m/s.