# Circular motion problem

A flatbed lorry travels at 100km/hr around a corner of radius 300m. inwardly banked at 10°
On the back of the lorry is a crate whose mass is 200kg. The cofficient of static fricition between the crate and the lorry being 0.7.

A) State the magnitude and direction (up or down the bed) of the frictional force F acting on the crate.

I am struggling with this question i believe you have to use the F= Mv^2/r to find the force but where does the static friction come into the equation?

B) If the lorry were to enter a corner with a bank angle of 40° and radius of 150m. what is the range of speeds over which the lorry may travel without the crate slipping?

Does this question require the use of the SUVAT equations?

Any working outs will be very useful

Thank you

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Simon Bridge
Homework Helper
Draw the free-body diagram (head on).
Draw all the forces acting on the load.

There must be a net unbalanced force pointing to the center of the turn equal to the centripetal force.

CWatters
Homework Helper
Gold Member
where does the static friction come into the equation
What stops the load sliding off the truck as it goes around the corner?

mv2/r is just one of the forces acting on the load. For example what other forces would act on the load if the truck was stationary on the banked road?

As Simon said draw the diagram and work out all the forces.

CWatters
Homework Helper
Gold Member
Part B is an variant of Part A. Won't need SUVAT equations.

Aside: Have you ever seen the banked track in a velodrome? The track is so steep that if a rider goes around too slowly they sometimes slide down the steep banking. On the other hand what would happen if you went around a banked track in a car way too fast or the banking wasn't steep enough? Under the right conditions there is a minimum and a maximum safe speed for banked tracks. Too slow and you slide down. Too high and you fly off the top. Your problem is similar except instead of friction between the tires and track being the issue is the friction between load and flat bed.