(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Ok I have been given an assignment and asked to answer questions about a lorry loaded and unloaded. the Text is as follows:

An unloaded lorry of mass M kg accelerates from rest and reaches a velocity of 30mph in 10 seconds. It then travels at constant velocity for half a minute before the driver applies the brakes and brings the vehicle to rest over a distance of D m.

The lorry is then loaded with 800 kg of building materials that need to be transported over a total distance of 0.6 km. After loading, the lorry accelerates over a distance of 80m to attain a velocity of 30mph again. The vehicle subsequently maintains constant velocity before decelerating to rest at a rate of R m/s2.

M=2300KG D = 70m R = 1.5m/s^2

2. Relevant equations

The questions exactly

Find for the unloaded lorry:

i) the force required to accelerate the vehicle, and the retarding force necessary to bring it to rest;

ii) the total time and the total distance travelled during this period.

Find for the loaded lorry :

i) the force required to accelerate the vehicle and the retarding force necessary to bring it

to rest;

ii) the total time taken during this period and the distance travelled at constant velocity.

c) Calculate the % change in the momentum of the lorry from loaded to unloaded, whilst travelling at the specified constant velocities.

d) Draw the ‘velocity-time’ graph of the motion of the lorry in its unloaded and loaded states, indicating clearly salient points and values.

3. The attempt at a solution

I tried using V^2 = U^2 +2as , V=S/t and general thinking but im 100% sure that im incorect. i got answers like 0.65 m/s^2 which seemed possible but it is half the acceleration than when the lorry was unloaded, i think half is too little if only 800KG was added. i also got stupid answers like 15.67 m/s^2

can some one help me

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# Homework Help: Simple question of acceleration

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