Question

The velocity-time graph below represents the velocity of a toy train as it moves north and south with velocity near the middle of the vertical axis. During which, Interval(s) is the toy train speeding up?

• A. $0toA$ only
• B. $0toA$ and $DtoE$
• C. $AtoB$
• D. $BtoD$ only
• E. $AtoB$ and $DtoE$

Answer 1

Answer: (B)

$0toA$ and $DtoE$

We know that slope of velocity-time graph with time axis gives the acceleration i.e. $a=dv/dt$ .

In the given graph ,

For time interval $B$ , the slope is zero so $a=0$ which implies ,

$dv/dt=0$ ,

or $v=constant$ ,

For time interval $A$ and $D$ , the slope is positive so $a=+ve$ which implies,

Velocity is increasing (speeding up) ,

For time interval $C$ and $E$ , the slope is negative so $a=-ve$

which implies deceleration i.e. velocity is decreasing .