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M1 help

Need help with the last part from question 3. I am not sure if the previous parts are right

Thanks :smile:
Your graph isn't quite right. I suggest working out how long it takes the man to finish the race, then use this to find the woman's speed throughout the race since her speed is constant. There you will find if the speed of the woman is the same/greater/smaller than the man's speed.
Reply 2
Original post by Protoxylic
Your graph isn't quite right. I suggest working out how long it takes the man to finish the race, then use this to find the woman's speed throughout the race since her speed is constant. There you will find if the speed of the woman is the same/greater/smaller than the man's speed.

For the time I did time= distance/speed for each section. Which gave me (120/1.5)+(180/4.5)+(60/1.5)=160s
Woman speed = 360/160= 2.25
So the man overtakes somewhere whilst running I think. Not sure how you work that out. Also what is wrong with the graph? Thanks :smile:
Original post by Super199
For the time I did time= distance/speed for each section. Which gave me (120/1.5)+(180/4.5)+(60/1.5)=160s
Woman speed = 360/160= 2.25
So the man overtakes somewhere whilst running I think. Not sure how you work that out. Also what is wrong with the graph? Thanks :smile:


Yes, so the women's speed is 2.25 and then man's is 1.5, so the women is faster than the man initially. Does your graph support this? What is the gradient on a (x,t) graph? Well in your case it's a (t,x) graph, I would first flip your axes around so t lies on the Y axis.
Reply 4
Original post by Protoxylic
Yes, so the women's speed is 2.25 and then man's is 1.5, so the women is faster than the man initially. Does your graph support this? What is the gradient on a (x,t) graph? Well in your case it's a (t,x) graph, I would first flip your axes around so t lies on the Y axis.

i thought the gradient of a displacement time graph was velocity. The gradient of (x,t) isn't anything is it?
Original post by Super199
i thought the gradient of a displacement time graph was velocity. The gradient of (x,t) isn't anything is it?


Ah sorry yes. I always draw my graphs as (x,t), it will probably confuse you if you do, it's just something I've gotten used to. So yes the gradient of your graph is velocity, so how should the gradient of the dotted line compare to the initial gradient of the man's trajectory if the women is moving faster than the man initially.
Reply 6
Original post by Protoxylic
Ah sorry yes. I always draw my graphs as (x,t), it will probably confuse you if you do, it's just something I've gotten used to. So yes the gradient of your graph is velocity, so how should the gradient of the dotted line compare to the initial gradient of the man's trajectory if the women is moving faster than the man initially.

it should be greater
Original post by Super199
it should be greater


Yes, now look at your line for the man. Since the man walks at the same speed at the end and at the start, they also should be the same gradient.
Reply 8
Original post by Protoxylic
Yes, now look at your line for the man. Since the man walks at the same speed at the end and at the start, they also should be the same gradient.

i see. I've sorted this question out now :smile: thanks for the help.
Original post by Super199
i see. I've sorted this question out now :smile: thanks for the help.


No problem:smile:

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