Natural frequency (resonance) : SHM problem, please help!?

Question

11) You are on a shopping spree, taking your 21-gear bicycle to the grocery shop. You head home with one full shopping bag on each handle bar, carefully balancing through the traffic. Everything goes well until you reach a climb through the outer gardens of your estate, where you must pedal hard. Suddenly, the bags start swinging violently, and you are about to lose control of the bike.

a) Give a physical explanation of what happens.

b) How can you keep up both appearances and speed? (i.e. how can you solve the problem without stopping or slowing down)

Thankyou very much if you answer this. It will be really gratefull and helpfull!

Answer 1

b) change gear, so you stop driving the bags at their natural frequency

Answer 2

(a) When you ride slowly through the traffic, the frequency of the vibration of your bike is far below the natural frequency of the bags, the forced oscillation on the bags is negligible.

When you are speeding up to climb the slope, the frequency of vibration increases closer and closer to the natural frequency of the bags, making them oscillate more vigorously.

When the vibration of the bike has the same frequency as the bags, the latters will be in resonance and swing violently.

(b) To keep up the speed and still control the vibration, you can change the gear as suggested above by Nobody