Question

A truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of 400 m in 20 s. Find its acceleration. Find the force acting on it if its mass is 7 tonnes

Answer 1

>acceleration = 2m/s²

>Force = 14,000N

Given :-

truck starts from rest

•°• Initial velocity u = 0

travel a distance of 400m

•°• distance s = 400m

time give = 20s

mass of the body = 7 tonnes

To find :-

Acceleration,

Force

Solution:-

it is given that,

u= 0

s = 400m

t = 20s

Applying formula :-

s= ut + 1/2 at²

400 = 0(20) + 1/2(a)(20)²

400= 0 + 1/2(a)(400)

400= 200 x a

or,

a = 400/200 = 2

therefore,

acceleration = 2m/s²

Now,

We know that

F= m x a

firstly, we have to convert tonnes to kg

= 1 tonnes = 1000kg

•°• 7 tonnes = 7000kg

Now, putting it on formula

=> F = 7000 x 2 = 14,000 N

Hence,

Force = 14,000N

Answer 2

Explanation:

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Time = 20 seconds

1) We have to find the acceleration of the truck.

So, from the equation of motion S =

$ut \: + \: \frac{1}{2} \: a \: \times \: {t}^{2}$

Where u = 0

$S \: = \frac{1}{2} a \: \times \: {t}^{2} \\ \\ a = \frac{2 \times S}{ {t}^{2} } = \frac{2 \times 400}{20 \times 20} = 2 \frac{m}{ {sec}^{2} }$

2) Force acting on truck.

So, from Newton's 2nd law of motion.

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F = ma = 7000 × 2 = 14,000 = 14kN