A train moving at 72 km/h applies brakes and comes to a stop in 5 seconds. What

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Question: A train moving at 72 km/h applies brakes and comes to a stop in 5 seconds. What is the deceleration? (2023)

Options:

Correct Answer: 4 m/s²

Solution:

First convert speed to m/s: 72 km/h = 20 m/s. Deceleration = (final velocity - initial velocity) / time = (0 - 20) / 5 = -4 m/s².

A train moving at 72 km/h applies brakes and comes to a stop in 5 seconds. What is the deceleration? (2023)

A train moving at 72 km/h applies brakes and comes to a stop in 5 seconds. What is the deceleration? (2023)

Step 1: Convert the speed from kilometers per hour (km/h) to meters per second (m/s). Use the conversion factor: 1 km/h = 1/3.6 m/s. So, 72 km/h = 72 / 3.6 = 20 m/s.
Step 2: Identify the initial velocity (speed before braking) and the final velocity (speed after stopping). The initial velocity is 20 m/s and the final velocity is 0 m/s.
Step 3: Use the formula for deceleration: Deceleration = (final velocity - initial velocity) / time. Plug in the values: Deceleration = (0 - 20) / 5.
Step 4: Calculate the deceleration: Deceleration = -20 / 5 = -4 m/s².

Unit Conversion – Converting speed from kilometers per hour to meters per second is essential for consistent units in calculations.
Deceleration Calculation – Understanding how to calculate deceleration using the formula (final velocity - initial velocity) / time.