Question

Question 5 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 metric tonnes (Hint: 1 metric tonne = 1000 kg).

Class 9 - Science - Force and Laws of Motion Page 128

Answer 1

HI !

Initial velocity =u = 0
Distance =s = 400 m
time = t= 20 sec

a = acceleration

Equation of motion :-

s = ut + 1/2at²

400 = 0 + 1/2 × a × 20 × 20

400 = 200 a
a = 2


acceleration = a = 2 m/s²
============================

Force = F
Mass = m = 7000 kg
Acceleration = a = 2 m/s²

F = ma
= 7000 × 2
= 14000 N

Force acting on it is 14000 N

Answer 2

hey mate....

u = 0
s = 400 m
t = 20 second
m = 7 ✖ 1000 = 7,000 kg. (1 tonne = 1,000kg )
a =?
F=?
soo
s = ut +1/2 at square
put given numbers
400=0+1/2 a(20)square
=400/200
=2 m/s square
........now
F = m ✖ a
= 7,000 ✖ 2
= 14,000 N