Question

1
A car of mass 3000 kg is moving with a velocity of 10 ms. If the velocity-time graph for this car is
a horizontal line parallel to the time axis, then the velocity of the car at the end of 25 s will be:
(a) 40 m/s
(c) 10 m/s
(d) 250 m/s​

Answer 1

Answer :

Mass of car = 3000kg

Initial velocity = 30m/s

Velocity → time graph for this car is a horizontal line parallel to the time axis.

We have to find velocity of the car at the end of 25s$.$

★ Graph :

$\setlength{\unitlength}{1cm}\begin{picture}(5,5)\linethickness{0.4mm}\put(0,0){\vector(1,0){5}}\put(1,-1){\vector(0,1){5}}\put(1,2){\line(1,0){2.5}}\put(0.4,3.8){\bf v}\put(5.3,0){\bf t}\end{picture}$

We know that, slope of velocity → time graph gives acceleration.

ATQ, slope of graph is zero it means that car has not acceleration.

First equation of kinematics :

• v = u + at

v denotes final velocity

u denotes initial velocity

a denotes acceleration

t denotes time

➠ v = u + at

➠ v = 10 + (0)(25)

➠ v = 10 + 0

➠ v = 10m/s

∴ (C) is the correct answer!

★ Additional Information :

• Acceleration is defined as the rate of change of velocity.
• It is a vector quantity having both magnitude as well as direction.