Question

es is 2.8
8. A body is moving with a speed of 20 m/s. When a certain force is applied, an
acceleration of 4 m/sis produced. After how much time will its velocity become
80 m/s?
​

Answer 1

Answer:

15 sec

Explanation:

V-U/t = a

80 - 20/t =4

t=60/4

t= 15

So ans is 15 secs

Answer 2

Given:-

• Initial velocity, u = 20m/s
• Acceleration, a = 4m/s²
• Final velocity, v = 80m/s

To Find:-

• After how much time will its velocity become 80 m/s?

Solution : -

$\qquad$ ☀️To calculate it we will use the 1st equation of motion.We know that 1st equation of motion :-

$\qquad$ ⎘ $\blue{\pmb {\mathfrak{v = u + at}}}$

$\qquad\small\underline{\pmb{\sf Substituting \: the\: given\: values \::-}}$

$\pink{\qquad\leadsto\quad \pmb {\mathfrak{ v = u + at}}}$

$\qquad\leadsto\quad \pmb {\mathfrak{ 80 = 20 + 4 \times t}}$

$\qquad\leadsto\quad \pmb {\mathfrak{ 80 - 20 = 4t}}$

$\qquad\leadsto\quad \pmb {\mathfrak{ 60 = 4t}}$

$\qquad\leadsto\quad \pmb {\mathfrak{ t =\cancel{ \dfrac{60}{4}}}}$

$\pink{\qquad\leadsto\quad \pmb {\mathfrak{ t = 15\; sec}}}$

• After 15 sec body's velocity will be 80 m/s.

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$\qquad$☀️Equations of motion :-

$\qquad$ ⑴ v = u + at

$\qquad$ ⑵ s = ut + ½at²

$\qquad$ ⑶ v² - u² = 2as

• v = final velocity
• u = initial velocity
• s = displacement
• t = time taken
• a = acceleration

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