Question

A boat in a race accelerates uniformly at 0.2 m/s² for 18 seconds to reach a final speed of 6 m/s. Work out the initial speed of the boat.

Answer 1

Given:-

• Acceleration , a = 0.2m/s²

• Time taken,t = 18s

• Final velocity ,v = 6m/s

To Find:-

• Initial velocity of the boat ,u.

Solution:-

By using 1st equation of motion

• v = u+at

Substitute the value we get

→ 6 = u + 0.2×18

→ u = 6/3.6

→ u = 1.66 m/s

Additional Information !!

Some equation of motion are

• v = u +at

• s = ut +1/2at².

• v² = u² + 2as

Here,

v is the final velocity

u is the initial velocity

a is the acceleration

s is the displacement or Distance

t is the time taken

Answer 2

Explanation:

Let v,t

1

,t

2

be the maximum velocity attained, time for which car accelerated and the time for which car retarded respectively

⇒t

1

=(v−u)/a=(v−0)/2=v/2

⇒t

2

=(v−u)/a=(0−v)/(−4)=v/4

Now it is given that,

⇒t

1

+t

2

=3

⇒v/2+v/4=3

⇒v=4m/s

Hence correct answer is