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Physics Velocity time graph help

Jerome

New member
May 15, 2013
17
A train starts from rest from a station and travels with uniform acceleration 0.5m/s^2 for 20s. it travels with uniform velocity for another 30s, the brakes are then applied so that a uniform retardation is obtained and the train comes to rest in a further 10s. sketch the velocity-time graph of this motion. Using your graph, calculate the total distance travelled by the train

please can i see the graph, and also include explanation so that i can understand better
 

MarkFL

Administrator
Staff member
Feb 24, 2012
13,775
First, let me ask you if the velocity changes uniformly, that is, the acceleration is constant, how will the velocity vary, mathematically speaking?
 

Jerome

New member
May 15, 2013
17
i don't have answers to that.
 

Klaas van Aarsen

MHB Seeker
Staff member
Mar 5, 2012
8,905
Welcome to MHB, Jerome! :)

A train starts from rest from a station and travels with uniform acceleration 0.5m/s^2 for 20s. it travels with uniform velocity for another 30s, the brakes are then applied so that a uniform retardation is obtained and the train comes to rest in a further 10s. sketch the velocity-time graph of this motion. Using your graph, calculate the total distance travelled by the train

please can i see the graph, and also include explanation so that i can understand better
i don't have answers to that.
The formula for velocity with uniform acceleration is:
$$v = v_0 + a t$$
where $v$ is the speed at time $t$, $v_0$ is the initial speed, and $a$ is the uniform acceleration.

Is this formula known to you?

Anyway, in your problem, we can deduce that $v_0 = 0$, since the train is initially at rest.
And $a=0.5 m/s^2$ is given.

Do you know how to draw the graph of $v=0.5 t$ for the time period of 0 to 20s?
What will be the speed at $t=20s$?
 

Jerome

New member
May 15, 2013
17
Welcome to MHB, Jerome! :)





The formula for velocity with uniform acceleration is:
$$v = v_0 + a t$$
where $v$ is the speed at time $t$, $v_0$ is the initial speed, and $a$ is the uniform acceleration.

Is this formula known to you?

Anyway, in your problem, we can deduce that $v_0 = 0$, since the train is initially at rest.
And $a=0.5 m/s^2$ is given.

Do you know how to draw the graph of $v=0.5 t$ for the time period of 0 to 20s?
What will be the speed at $t=20s$?

i got that thanks, the graph looks like a trapezium, so the area of the trapezium is the total distance right?
 

Klaas van Aarsen

MHB Seeker
Staff member
Mar 5, 2012
8,905
i got that thanks, the graph looks like a trapezium, so the area of the trapezium is the total distance right?
Yep!