Question

truck is moving with a velocity of 20 m.s-1. Upon instruction by a traffic policeman, the truck stops in 8 seconds.
i. Calculate the acceleration of the truck
ii. Determine the distance travelled by the truck form the moment the instruction was given
till the moment it stopped

Answer 1

GIVEN:

• Initial Velocity (u) of truck = 20 m/s
• Final velocity (v) of truck = 0 [the truck stop]
• Time taken by the truck = 8 seconds

TO FIND:

• What is the acceleration and Distance covered by the truck ?

SOLUTION:

Let the acceleration of the truck be 'a' m/s²

❶ We have to find the acceleration of the truck

To find the acceleration of the truck, we use the formula:-

❰ a = $\bf{\dfrac{v -u}{t}}$ ❱

According to question:-

➜ a = $\sf{\dfrac{0 - 20}{8}}$

➜ a = $\sf{\cancel\dfrac{-20}{8}}$

❮ a = –2.5 m/s² ❯ [Retardation]

❷ We have to find the distance travelled by the truck

To find the distance of the truck, we use the second Equation of motion:-

❰ s = ut + $\bf{\dfrac{1}{2}}$ at² ❱

According to question:-

➜ s = 20 $\times$ 8 + $\sf{\dfrac{1}{2}}$ $\times$ –2.5 $\times$ (8)²

➜ s = 160 –2.5 $\times$ 32

➜ s = 160 –80

❮ s = 80 m ❯

❝ Hence, the acceleration is –2.5 m/s² and distance travelled by the truck is 80 m ❞

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