Question

1. A moving train brought to rest within 20 s by applying brakes. If the retardation due to brakes is 2 m/s2, then find the initial velocity of the train

Answer 1

v = 0
t=20s
a = -2m/s2
u = ?
v =u+at
0 = u + - 2m/s2 × 20s
0 = -40 m/s
u = 40m/s

Answer 2

Answer :

Given -

• t = 20 s
• v = 0 m/s
• a = -2 m/s

To Find -

• u = ?

Solution -

We know that, v = u + at.

Using it to find u,

⇒ 0 = u + (-2)(20)

⇒ -u = -40

⇒ u = 40 m/s

Additional Information -

• Speed is the total distance travelled per unit time.
• Velocity is displacement per unit time.
• Speed is a scalar quantity whereas velocity is a vector quantity.
• Distance is a scalar quantity whereas displacement is a vector quantity.
• Distance is the total length of the path travelled by a body.
• Displacement the shortest distance between the initial position and the final position of the body.