Question

A truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of 400m in 20s. Find the acceleration. Find the force acting on it if its mass is 7 tonnes. (Hint: 1 tonne = 1000 kg.)

Answer 1

Answer:

u = 0

s = 400 m

t = 20 s

According to Newton's 2nd law of motion,

s = ut+1/2at²

400 = 0×20+1/2×a×(20)²

400 = a/2 × 400

400 = 200a

a = 400/200

a = 2 m/s²

F = ma

F = 7 tonnes × 2 m/s²

F = 7000 kg × 2 m/s²

F = 14000 kg m/s²

F = 14000 N

Acceleration = 2m/s²

Force = 14000 N

Answer 2

Answer:

• Acceleration,a = 2ms^-2

• Force,f = 1400N

Explanation:

Given :

• Initial velocity of the truck,u => 0 [Since truck starts from rest]
• Distance travelled,s => 400m
• Time taken,t => 20s
• Mass,m => 7 tonnes = (7 × 1000)kg = 7000kg

To Find :

• Accelaration,a => ?
• Force,f => ?

Solution :

We know that :-

$\rm{s=ut+\dfrac{1}{2}at^2$

$\rightarrow\rm{400m=0\times 20s+\dfrac{1}{2}\times a\times(20)s^2$

$\rightarrow \rm{400m=0+\dfrac{1}{2}\times a\times400s^{2}$

$\rightarrow\rm{}400m=\dfrac{1}{1}\times a\times 200s^2$

$\rightarrow\rm{400m=a\times200s^2}$

$\rightarrow \rm{a=\dfrac{400m}{200s^2}$

$\rightarrow\rm{a=2ms^{-2}}$

Force = m × a

⇒ F = 7000kg × 2ms^-2

⇒ F = 1400N