Question

Initially stationary, a train has a constant acceleration of 0.9 m/s2.

Answer 1

The speed after 21 s is 18.9 m/s and the total time required for the train to reach a speed of 34 m/s is 14.4 s

What is Speed ?

Speed is a distance travelled by a body per time taken. It is a scalar quantity and it is measured in m/s

Given that at Initially stationary, a train has a constant acceleration of 0.9 m/s2.

(a) What is its speed after 21 s?

• Initially at rest, u = 0

• Acceleration a = 0.9 m/s²

• Time t = 21s

Using v = u + at

Substitute all the parameters into the equation

v = 0 + 0.9 x 21

v = 18.9 m/s

(b) What is the total time required for the train to reach a speed of 34 m/s?

Let first calculate for total distance by using

v² = u² + 2as

34² = 18.9² + 2 × 0.9 × S

1156 = 357.21 + 1.8S

1.8S = 1156 - 357.21

1.8S = 798.79

S = 798.79 / 1.8

S = 443.8 m/s

v = u + at

34 = 21 + 0.9t

0.9t = 34 - 21

0.9t = 13

t = 13/0.9

t = 14.44s

Therefore, its speed after 21 s is 18.9 m/s and the total time required for the train to reach a speed of 34 m/s is 14.4 s

Learn more about Speed here: brainly.com/question/24739297

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