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M1 question

The Q is a Mens race is 60m long, and was carried out in 6.41s.Assuming the race was carried out under constant acceleration, calculate the acceleration of the runner and his speed at the end of the race?

I kinda forgot what constant acceleration means, I just thought I dont have enough info to work out anything?
Constant acceleration means you can use suvat equations

you know s, u and t
Reply 2
Avatar for Zacken
Zacken
22
Original post by SunDun111
The Q is a Mens race is 60m long, and was carried out in 6.41s.Assuming the race was carried out under constant acceleration, calculate the acceleration of the runner and his speed at the end of the race?

I kinda forgot what constant acceleration means, I just thought I dont have enough info to work out anything?


Constant acceleration means you can use SUVAT.

You know:

s=60
u=0 (has to start from rest, it's a race)
v=?
a=?
t=6.41

So what equations can you use to find a? s = ut + 1/2at^2 seems pretty useful to me...
Reply 3
Avatar for SunDun111
SunDun111
OP
11
Original post by Zacken
Constant acceleration means you can use SUVAT.

You know:

s=60
u=0 (has to start from rest, it's a race)
v=?
a=?
t=6.41

So what equations can you use to find a? s = ut + 1/2at^2 seems pretty useful to me...

Ok thanks
Reply 4
Avatar for SunDun111
SunDun111
OP
11
Original post by Zacken
Constant acceleration means you can use SUVAT.

You know:

s=60
u=0 (has to start from rest, it's a race)
v=?
a=?
t=6.41

So what equations can you use to find a? s = ut + 1/2at^2 seems pretty useful to me...


Ok I worked out the acceleration as 2.93, and the speed he finished the race as 18.73ms but the next part of the question says, assume that in a 100m race the runner accelerates for the next 60m and completes the race by running the next 40m in the speed you calculated for the end of the 60m. Calculate the time for the athlete to complete the race.

I would think you have to use SUVAT just for the final 40m? But would U = 0?
Reply 5
Avatar for Zacken
Zacken
22
Original post by SunDun111
Ok I worked out the acceleration as 2.93, and the speed he finished the race as 18.73ms but the next part of the question says, assume that in a 100m race the runner accelerates for the next 60m and completes the race by running the next 40m in the speed you calculated for the end of the 60m. Calculate the time for the athlete to complete the race.

I would think you have to use SUVAT just for the final 40m? But would U = 0?


No... if he runs the next 40m at a speed of 18.73, then it's literally just time = distance/speed = 40/18.73
Reply 6
Avatar for SunDun111
SunDun111
OP
11
Original post by Zacken
No... if he runs the next 40m at a speed of 18.73, then it's literally just time = distance/speed = 40/18.73


Thanks done it, another Q us a sprinter starts from rest, accelerates at 2ms and for the frist four seconds of the race the sprinter moves along a strraight line. Find the distance travelled byt the sprinter in the first 4 seconds, find the speed of the sprinter at the end of the first 4 seconds, the sprinter travels at this speed for the remainder of the race, he travels a total distance of 100m find the total time that he takes th complete the way.

I got the distance as 16m and speed after 4 seconds as 8ms. But I cant do the final bit, how would i break it down?
Reply 7
Avatar for Zacken
Zacken
22
Original post by SunDun111
Thanks done it, another Q us a sprinter starts from rest, accelerates at 2ms and for the frist four seconds of the race the sprinter moves along a strraight line. Find the distance travelled byt the sprinter in the first 4 seconds, find the speed of the sprinter at the end of the first 4 seconds, the sprinter travels at this speed for the remainder of the race, he travels a total distance of 100m find the total time that he takes th complete the way.

I got the distance as 16m and speed after 4 seconds as 8ms. But I cant do the final bit, how would i break it down?


If he's already travelled 16 metres in 4 seconds, it means he has 100 - 16 metres left that he runs at 8 metres per second.

So how long does he take to run (100-16) metres at 8 metres per second? Same formula. Time = distance/speed.

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