**Question 6: **Explain why do buses and heavy trucks have large steering wheels?

Answer

Heavy trucks and buses have more masses. From the law of inertia, we know that if a body has more mass it is difficult to change its state of rest or state of uniform motion.

The steering wheel is used to change the direction of motion of the vehicle. Changing direction is obviously a change in the state of the uniformly moving vehicle. In case of such heavy vehicles, more torque (force) will be required to change its direction. Torque is given by the mathematical equation

The equation clearly says that greater value of ‘r’ will produce more torque with less force. Larger wheels have larger values of ‘r’ (radius) hence more torque is produced with comparatively less force. Therefore, buses and trucks and other heavy vehicles have larger steering wheels to turn them easily. If the wheels were small, the driver would have to exert a lot of force while turning the vehicle.

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