Hi I'm having trouble with this problem and was wondering if anyone could help point me in the right direction.(adsbygoogle = window.adsbygoogle || []).push({});

1. The problem statement, all variables and given/known data

An experimental rocket-car of mass 1000 kg is at rest on a road that is inclined at 10 degrees to the horizontal. The driver starts the engine and releases the brakes and accelerates the rocket car down the slope for 9s. At that point the engine stops and a rear end parachute opens rapidly slowing the vehicle. (Shown in graph in attachment)

Estimate the rocket car's acceleration at t=9.1s immediately after the parachute opens

Using this answer, find

i) the net force down the slope

ii) the total resistive force (due to air resistance, friction etc)

at 9.1 s after the engine stops

2. The attempt at a solution

To find the acceleration at 9.1s, I would have to draw a tangent to that point on the graph and then find the slope of the tangent. Would this be correct?

i) to calculate the net force down the slop would this simply be

F=ma

m-mass of the rocket car, 1000kg

a- acceleration at 9.1s from the previous answer?

ii) I have no idea how to find the total resistive force. Can anyone give me any hints to start me off?

Thanks

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# Homework Help: Velocity Time Graph to calculate resistive forces

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