Final answer:
When an object is dropped from a height, it accelerates due to gravity until it reaches its maximum speed or terminal velocity. The time it takes to reach a speed of 45km/h can be calculated using the equations of motion.
Step-by-step explanation:
This question is about the motion of an object in free fall. When an object is dropped from a height, it accelerates due to gravity until it reaches its maximum speed or terminal velocity. The time it takes to reach a certain speed can be calculated using the equations of motion.
The acceleration due to gravity is approximately 9.8 m/s^2. To convert 45 km/h to m/s, we multiply by 1000/3600 = 5/18. So, the speed is approximately 12.5 m/s.
Using the equation v = u + at, where v is the final velocity, u is the initial velocity (0 m/s), a is the acceleration, and t is the time, we can rearrange the equation to solve for t:
t = (v - u) / a = (12.5 - 0) / 9.8 ≈ 1.28 s
Therefore, it takes approximately 1.28 seconds for the object to reach a speed of 45 km/h.
It is important to note that the final velocity and distance traveled during the first and last seconds of motion depend on various factors such as initial height, air resistance, and the shape and mass of the object. The calculations provided assume ideal conditions with negligible air resistance.