A train moving at 72 km/h applies brakes and comes to a stop in 10 seconds. What

Practice Questions

Q1
A train moving at 72 km/h applies brakes and comes to a stop in 10 seconds. What is the acceleration of the train?
  1. -2 m/s²
  2. -3 m/s²
  3. -4 m/s²
  4. -5 m/s²

Questions & Step-by-Step Solutions

A train moving at 72 km/h applies brakes and comes to a stop in 10 seconds. What is the acceleration of the train?
  • Step 1: Convert the speed from kilometers per hour (km/h) to meters per second (m/s). To do this, 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 speed (u) and final speed (v). The initial speed (u) is 20 m/s (the speed of the train before braking), and the final speed (v) is 0 m/s (the train comes to a stop).
  • Step 3: Determine the time (t) it takes for the train to stop. In this case, t = 10 seconds.
  • Step 4: Use the formula for acceleration (a): a = (v - u) / t. Plug in the values: a = (0 - 20) / 10.
  • Step 5: Calculate the acceleration: a = -20 / 10 = -2 m/s². The negative sign indicates that the train is decelerating.
  • Kinematics – Understanding the relationship between speed, time, and acceleration.
  • Unit Conversion – Converting speed from kilometers per hour to meters per second.
  • Acceleration Calculation – Applying the formula for acceleration based on initial and final velocities over time.
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