4. Brick A is hurled vertically upward from a bridge at an initial speed of 4.90 m/s. One second later, Brick B is thrown horizontally from the same bridge with an initial speed of 9.80 m/s. Which hits the water first?
To determine which brick hits the water first, we need to analyze their vertical motion separately.
Let's start with Brick A. It is thrown vertically upward with an initial speed of 4.90 m/s. The acceleration due to gravity is always acting downward (negative direction) and is approximately 9.8 m/s^2. Since Brick A is moving against gravity, its vertical velocity decreases until it reaches its highest point and starts coming down.
To find out when Brick A hits the water, we can use the equation of motion:
v = u + at
where:
v = final velocity (0 m/s, since the brick comes to rest)
u = initial velocity (4.90 m/s)
a = acceleration (-9.8 m/s^2)
t = time
Since we're looking for the time it takes for Brick A to hit the water, we set v = 0 and solve for t:
0 = 4.90 - 9.8t
9.8t = 4.90
t = 4.90 / 9.8
t = 0.5 seconds
Now let's consider Brick B, which is thrown horizontally. Since there is no vertical force acting on it, it will follow a straight horizontal path and will not be affected by gravity in this direction.
This means the time it takes for Brick B to hit the water will only depend on its horizontal velocity. Since it is thrown with an initial speed of 9.80 m/s, it will take the same time as Brick A (0.5 seconds) to reach the water.
Therefore, both bricks will hit the water at the same time.