A boy pushes a box of mass 2 kg with a force $\vec{F}=(20 \hat{i}+10 \hat{j}) \mathrm{N}$ on a frictionless surface. If the box was initially at rest, then ____ m is displacement along the x -axis after 10 s .

JEE Main · 2021 · 26 Feb 2021 · Shift 1 · Kinematics

A boy pushes a box of mass 2 kg with a force

F = (20 \hat{i} + 10 \hat{j}) N

on a frictionless surface. If the box was initially at rest, then ____ m is displacement along the x -axis after 10 s .

Answer: 500

Solution

The force component along the x-axis is

F_{x} = 20

N. Using Newton's second law:

a_{x} = \frac{F _{x}}{m} = \frac{20}{2} = 10

m/s². Since the box starts from rest, using the kinematic equation

s = u t + \frac{1}{2} a t^{2}

with

u = 0

a = 10

m/s², and

t = 10

s_{x} = 0 + \frac{1}{2} (10) (10)^{2} = 5 \times 100 = 500

JEE Main · 2021 · 26 Feb 2021 · Shift 1 · Integer answer

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