Question

a train travels 20 m/sec and takes 5 seconds to slow to 10 m/sec.
what is the trains acceleration?
oa $a=\frac{(0 - 20)}{5}=-4\\ m/sec^{2}$
ob $a=\frac{(10 - 20)}{5}=-2\\ m/sec^{2}$
oc $a=\frac{(20 - 10)}{5}=2\\ m/sec^{2}$
od $a=\frac{(20 - 0)}{5}=4\\ m/sec^{2}$

Explanation:

Step1: Recall the acceleration formula

The formula for acceleration is \(a=\frac{v - u}{t}\), where \(v\) is the final velocity, \(u\) is the initial velocity, and \(t\) is the time.

Step2: Identify the values

Here, \(u = 20\space m/sec\), \(v=10\space m/sec\), and \(t = 5\space sec\).

Step3: Substitute the values into the formula

Substitute the values into \(a=\frac{v - u}{t}\), we get \(a=\frac{10 - 20}{5}\).
Calculate the numerator: \(10-20=- 10\).
Then \(a=\frac{-10}{5}=-2\space m/sec^{2}\).

Answer:

B. \(a=\frac{(10 - 20)}{5}=-2\space m/sec^{2}\)