A bicycle (with rider) is speeding up. In which direction does the friction act on the front wheel? On the rear wheel? Don't use your gut instinct. Instead, justify your answer based on physical principles.
After thinking about the initial question for a few moments I actually came to the correct conclusion for each of the frictional force vectors. The frictional force that acts on any body is commonly pointing in the opposite direction of motion or intended motion --- a stationary block on an incline remains motionless because friction points opposite to how it would slide. Taking the bike's front wheel off the bike and allowing it to roll on its own (assuming it remains vertical) one would expect the wheel to eventually slow to a stop, hence friction points to the left for the front wheel. As for the rear wheel, if one considers the wheel to be on ice it would just spin (while pedaling), so the motion for the bottom point is to the left, hence friction must be to the right. But while coasting both wheels will have friction pointing to the rear, since the rear wheel becomes just like the front.
Sir I would like to thank you I found this video very helpful in terms of the way you explained it with principles, however what i would like to understand based on the permutation u have told us to consider for a case where the bicycle slows down or the brakes are rapidly applied(assuming the wheels lock/slide) or in lamens terms the wheel rolls with slipping would the frictional force on the rear wheel be in the same direction as it is in your video lecture analysis or would it differ and why.
cant we say the point touching the ground have a tendency to move in left direction so the net force at that point is in just opposite drxn and since only friction is there at that point....hence friction is in right
Sir, allow me to ask why we do not include the force of the driving torque (let's call it Ft) in the set of equations, the direction of it will be opposite of the bycicle direction right?
