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# A train with an initial velocity of 20ms-1 is subjected to a uniform deceleratio...

### Question

A train with an initial velocity of 20ms-1 is subjected to a uniform deceleration of 2ms-2. The time required to bring the train to a complete halt is

A) 10s

B) 40s

C) 5s

D) 20s

### Explanation:

We have been given:
final velocity = $$v = 0\text{m/s}$$, initial velocity = $$u = 20\text{m/s}$$, deceleration = $$a = -2\text{m/s}^2$$ (this value is negative because it is decelerating)
$$v = u + at$$
$$0=20+(-2t)$$
$$2t=20$$
$$t=20÷2=10\text{s}$$

## Discussion (3)

• We have been given:
final velocity = $$v = 0\text{m/s}$$, initial velocity = $$u = 20\text{m/s}$$, deceleration = $$a = -2\text{m/s}^2$$ (this value is negative because it is decelerating)
$$v = u + at$$
$$0=20+(-2t)$$
$$2t=20$$
$$t=20÷2=10\text{s}$$

• Iyanuoluwa Ajibola

v = u + at
where v= final velocity = 0
u = initial velocity = 20m/s
a = retardation = 2m/s²
From the formula:
v = u + at
v - u = at
0 - 20 = 2t
-20 = 2t
Divide both side by co-efficient of T
t = -20/2
t = 10s
Since deceleration is negatively virtual 2
I mean -2.

$$v = 0\text{m/s}$$, $$u = 20\text{m/s}$$, $$a = -2\text{m/s}^2$$ (the figure is carrying a negative sign because it is decelerating)
$$v = u + at$$
$$0=20+(-2t)$$
$$2t=20$$
$$t=20÷2=10\text{s}$$