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# URGENT) m1 projectiles help!!

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1. Hi,

on the june 2007 paper for AQA M1B no. 7,

there is a projectile question

An arrow is fired from a point A with a velocity of 25 m s1 , at an angle of 40 above thehorizontal. The arrow hits a target at the point B which is at the same level as the point A,as shown in the diagram.

a) State two assumptions that you should make in order to model the motion of the arrow.(2 marks)

(b) Show that the time that it takes for the arrow to travel from A to B is 3.28 seconds,correct to three significant figures. (4 marks)

(c) Find the distance between the points A and B. (2 marks)

(d) State the magnitude and direction of the velocity of the arrow when it hits the target.(2 marks)

(e) Find the minimum speed of the arrow during its flight

I've done all except d and e. what i did for d was to find the velocity of the arrow when it hits the target by using v=u+at (and subbing the time 3.28s into it)

but in the mark scheme it just says 25m/s, 40 degrees below horizontal. and I dont understand how?

also for e) how and when do we know what the minimum speed??

2. (Original post by liemluji)
Hi,

on the june 2007 paper for AQA M1B no. 7,

there is a projectile question

An arrow is fired from a point A with a velocity of 25 m s1 , at an angle of 40 above thehorizontal. The arrow hits a target at the point B which is at the same level as the point A,as shown in the diagram.

a) State two assumptions that you should make in order to model the motion of the arrow.(2 marks)

(b) Show that the time that it takes for the arrow to travel from A to B is 3.28 seconds,correct to three significant figures. (4 marks)

(c) Find the distance between the points A and B. (2 marks)

(d) State the magnitude and direction of the velocity of the arrow when it hits the target.(2 marks)

(e) Find the minimum speed of the arrow during its flight

I've done all except d and e. what i did for d was to find the velocity of the arrow when it hits the target by using v=u+at (and subbing the time 3.28s into it)

but in the mark scheme it just says 25m/s, 40 degrees below horizontal. and I dont understand how?

also for e) how and when do we know what the minimum speed??

d) Question says state, so no working is required. You should know that the flight path of a projectile is parabolic, so when it comes back to the same height it's velocity will be as before and angle of flight same as before except it's downwarrds rather than upwards.

e) Minimum speed:
Horizontal speed is unchanged throughout, so minimum speed will be when the vertical speed is minimum, i.e. when it is zero, at the max height (though you don't need that for the question as it only asks for the minimum speed, which will be the horizontal speed).
3. (Original post by ghostwalker)
d) Question says state, so no working is required. You show know that the flight path of a projectile is parabolic, so when it comes back to the same height it's velocity will be as before and angle of flight same as before except it's downwarrds rather than upwards.

e) Minimum speed:
Horizontal speed is unchanged throughout, so minimum speed will be when the vertical speed is minimum, i.e. when it is zero, at the max height (though you don't need that for the question as it only asks for the minimum speed, which will be the horizontal speed).
Wow! thank you! I tried to find it in the textbook but I couldn't but you've explained it very clearly thank you so much!

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