Question

Question 33:
(a) Explain the meaning of the following equation of motion :v = u + at, where symbols have their usual meanings.
(b) A body starting from rest travels with uniform acceleration. If it travels 100 m in 5 s, what is the value of acceleration ?

Lakhmir Singh Physics Class 9

Answer 1

Hi there !!
Here are your answers

1)
The first equation of Motion is v = u + at where ,
v = the initial velocity
u = the final velocity
a = acceleration
t = time taken
The 1st equation of motions shows that the final velocity is the product of acceleration and time added to the initial velocity.
This is similar to the formula to calculate acceleration but instead , here , the acceleration is uniform .
So,
$a = \frac{v - u}{t} \\ at = v - u \\ v = u \: + at$


2)
Given that ,
A body is starting from rest
So,
initial velocity (u) = 0m/s
Distance (s) = 100m
Time = 5sec
Let the acceleration be a

Using the 2nd equation of motion ,

s = ut + 1/2 at²

$100 = 0 + \frac{1}{2} \times a \times 25$

$\frac{100 \times 2}{25} = a$

a = 8

Thus,
the value of acceleration is 8m/s²


_________________

Hope it helps :D

Answer 2

v=final velocity
u=initial velocity
a=acceleration
t=time (answer of your 1st question)

2.
From 2nd equation
s=u+1/2at²
s=distance/displacement
u=initial velocity
a=acceleration
t=time
here,
s=100m
u=0
a=?
t=5sec
s=u+1/2at²
100=0+1/2×a×5²
100=0+1/2×a×25
100=0+1/2×25a
100×2÷25=a
200÷25=a
a=8
thus, acceleration=8m/sec²