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# couple of M1 q's for pos rep thanks watch

1. couple of M1 q's for pos rep thanks

edexcel M1 p104 question 2

2.)a car of mass 850 is towing a caravan of mass 550 along a level road. the engine of the car exerts a 4ward force of 2kN. the resistance to the motion of the car and caravan are proportional to there masses eg k x their masses, where k is a constant. given that the car accelerates at 0.5 ms-2 find the tension in the tow-bar

thanks
2. take free-body diagram:
forces on car are:
2000N forward and k.850 backward
2000 - 850k - T = 0.5x850

and forces on caravan are:
T - 550k = 0.5x550

2000 - 850k - T + T - 550k = 0.5 (850+550)
find k, then substitute in one of the equations and get T.
3. Using F=ma for;

Car:
2×103–T–850k = 850×0.5
2000–T–850k = 425 (1)

Caravan:
T – 550k = 550 × 0.5
T – 550k = 275 (2)

(1)+(2)
1400k = 2000 – 700
1400k=1300
14k=13
k=13/14

Sub k=13/14 back into (2)

T-550(13/14)=275
T- 7150/14=275
T=275+ 7150/14
T=785.7N
4. using f=ma for car:

2000-850k-T=850*0.5
2000-425-850k=T
T=1575-850k................. [1]

using f=ma for caravan:

T-550k=550*0.5
T=550k+275 ................. [2]

sub. for T:

1575-850k=550k+275
1575-275=55k+850k
1300=1400k
k=13/14

from [2]

T=(550* 13/14) +275
T=785.714
T=786 N (3s.f.)

hope that helps! (you need to draw diagram to understand completely)
5. thansk guys much appreciated

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