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kuzkasate
11-10-2012, 06:06 PM
I really need help on one of these physics questions, I just don't even know where to start?! Anyone who can help will get +rep so here's the question:

A car and caravan accelerate together at 0.5ms^-2.

(the car weighs 3000kg and the caravan weighs 5000kg)

a) Calculate the driving force of the engine
b) Calculate the tension in the tow bar
c) Calculate the resultant force on the car

Chippiewill
11-10-2012, 06:11 PM
a)

3000+5000 = 8000kg

F=ma
F= 8000 * 0.5 = 4000N

b) Draw clearly labelled force diagram for the caravan, only forces are Weight, Reaction Force and Tension.

Realise that the tension is causing the caravan to accelerate at 0.5ms^-2

Therefore T = 5000 * 0.5 = 2500N

c) Draw a clearly labelled diagram for the car, only forces are Weight, Reaction Force, Tension and Driving Force - This shows the tension going back at 2500N and the driving force going forwards at 4000N

Realise that Resultant Force = F-T = 4000-2500 = 1500N

kuzkasate
11-10-2012, 06:19 PM
a)

3000+5000 = 8000kg

F=ma
F= 8000 * 0.5 = 4000N

b) Draw clearly labelled force diagram for the caravan, only forces are Weight, Reaction Force and Tension.

Realise that the tension is causing the caravan to accelerate at 0.5ms^-2

Therefore T = 5000 * 0.5 = 2500N

c) Draw a clearly labelled diagram for the car, only forces are Weight, Reaction Force, Tension and Driving Force - This shows the tension going back at 2500N and the driving force going forwards at 4000N

Realise that Resultant Force = F-T = 4000-2500 = 1500N

Thank you so much! I tend to over complicate things in physics, I read the question and I'm like 'no.... that's too simple!' but you're a life saver - +repped!

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