Question

a freight train moving at an initial speed of 40 m/sec puts on its brakes, producing a deceleration of 0.50 m/sec. a. how long will it take thw train to travel next 100 m ? b. at what speed will it be traveling at the end of this 100 m ?

Answer 1

Answer on Question #63560, Physics / Quantum Mechanics

a freight train moving at an initial speed of $40\mathrm{m / sec}$ puts on its brakes, producing a deceleration of $0.50\mathrm{m / sec}$. a. how long will it take thw train to travel next $100\mathrm{m}$? b. at what speed will it be traveling at the end of this $100\mathrm{m}$?

Find: $t - ?v - ?$

Given:

$v_0 = 40.00 \, \text{m/s}$

$a = 0.50 \, \text{m/s}^2$

$s = 100 \, \text{m}$

Solution:

Movement is delayed.

Distance:

$-2as = v^2 - v_0^2$ (1)

Of (1) $\Rightarrow v^2 = v_0^2 - 2as$ (2)

Of (2) $\Rightarrow v = \sqrt{v_0^2 - 2as}$ (3)

Of (3) $\Rightarrow v = 37.73 \, \text{m/s}$

Acceleration:

$-a = \frac{v - v_0}{t}$ (4)

Of (4) $\Rightarrow t = \frac{v - v_0}{-a}$ (5)

Of (5) $\Rightarrow t = 2.54 \, \text{s}$

Answer:

a. $t = 2.54 \, \text{s}$

b. $v = 37.73 \, \text{m/s}$

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