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NEET PHYSICSEasy

A body of $5 \text{ kg}$ is moving with a velocity of $20 \text{ m/s}$ . If a force of $100 \text{ N}$ is applied on it for $10 \text{ sec}$ in the same direction as its velocity, what will now be the velocity of the body?

A

200 m/s

B

220 m/s

C

240 m/s

D

260 m/s

Step-by-Step Solution

Identify Given Data: Mass $m = 5 \text{ kg}$ , initial velocity $u = 20 \text{ m/s}$ , Force $F = 100 \text{ N}$ , time $t = 10 \text{ s}$ .
Method 1: Using Newton's Second Law and Kinematics

Calculate acceleration using Newton's Second Law: $a = \frac{F}{m} = \frac{100}{5} = 20 \text{ m/s}^2$ [Source 105, 126].
Use the first equation of motion: $v = u + at$ [Source 104].
$v = 20 + (20 \times 10) = 20 + 200 = 220 \text{ m/s}$ .

Method 2: Using Impulse-Momentum Theorem

Impulse $J = F \Delta t = 100 \times 10 = 1000 \text{ N s}$ .
Change in momentum $\Delta p = m(v - u)$ .
$1000 = 5(v - 20) \implies 200 = v - 20 \implies v = 220 \text{ m/s}$ [Source 131].

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