M1 question on s/t graphs!

A racing car is travelling on a straight horizontal road. Its inital speed is 25ms^-1 and it accelerates for 4s to reach a speed of V ms^-1. It then travels at a constant speed of V ms^-1 for a further 8s. The total distance travelled by the car during this 12s period is 600m.
a) draw a speed-time graph to illustrate the motion of this car during this 12s period.(done this)
b)Find the value of V.
c) find the acceleration of the car during the initial 4s period.

Reply 1

Malik

12

turtle2

A racing car is travelling on a straight horizontal road. Its inital speed is 25ms^-1 and it accelerates for 4s to reach a speed of V ms^-1. It then travels at a constant speed of V ms^-1 for a further 8s. The total distance travelled by the car during this 12s period is 600m.
a) draw a speed-time graph to illustrate the motion of this car during this 12s period.(done this)
b)Find the value of V.
c) find the acceleration of the car during the initial 4s period.

You know distance travelled=area under graph.

Look at my attachment.
To find area split that first part during the 4seconds into a triangle and rectangle.(triangle at the top, square at the bottom). You know the second part is just a big rectangle.So area is going to be:

(4 x 25) + ½(4 x (v-25)) + 8v =600m

solve that for the answer.

c) v=u+at
a=(v-25)/4 use value of v you get from part (b)

turtle.JPG5.0KB

Reply 2

bharatnakarja

Look at my attachment.
To find area split that first part during the 4seconds into a triangle and rectangle.(triangle at the top, square at the bottom). You know the second part is just a big rectangle.So area is going to be:

(4 x 25) + ½(4 x (v-25)) + 8v =600m

100 + 2v - 50 + 8v = 600
10v= 550
v=55

c) v=u+at
a=(v-25)/4
a=7.5

(edited 13 years ago)

M1 question on s/t graphs!

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