Why do passengers tend to fall sideways when the bus takes a sharp u turn? (2 marks)
2. Why should a passenger hold on to prevent himself from swaying in a turning bus? (2 marks)
3. Why do passengers tend to fall back when it starts suddenly? (2 marks)
4. Why do passengers jumping out of a rapidly moving bus fall forward with his face downwards, if he does not run forward? (2 marks)
5. Why does a passenger jumping out of a rapidly moving bus fall forward with his face downwards? (2 marks)
6. Why can dust be removed by shaking it, or beating it by a carpet? (2 marks)
7. Why does a bullet when fired against a glass window pane make a hole in it, and the glass pane will smash it? (2 marks)
8. Why does an athlete take a longer jump if he comes running from a distance than when he jumps suddenly from the take-off line? (2 marks)
9. What happens when you shake a wet piece of cloth? Explain, why? (2 marks)
10. Why is it advised to tie a rope on the luggage while you travel by the bus? (2 marks)
11. How does a boat move forward into the water when the boatman presses one end of the pole against the ground? (2 marks)
12. Why is it difficult for a fireman to hose, which ejects large amount of water at a high velocity? (3 marks)
Answers
1. When a bus takes a turn, the bus experiences a centrifugal (centre seeking) force which keeps the bus on the road. But due to inertia, the passengers are still in straight motion. Thus the passengers go sideways while the bus takes a U turn due to inertia.
2. (Read explanation for q.1)... Since the bus experiences a center seeking force, a passenger can hold to the bus to avoid the inertia that will make him sway sideways.
3. By Newton's law of inertia, a body remains to be in state of motion or rest unless acted upon by an external force. When a bus starts suddenly, passengers are at state of rest. Even though bus moves forward, inertia tries to keep passengers in rest state.
4. When passengers jump from a moving bus, their body is in state of motion. But ground on which they jump is in state of rest. So their feet come to rest but rest of the body remains in motion and passenger falls on the face. If he runs forward, he keeps his body in state of motion to avoid falling
5. Same as q.4
6. Dust is very light and does not get attracted to any body. It only settles on the top of any object and remain at rest due to inertia as long as object remains at rest. Thus it can be removed only by beating or shaking.
7. A bullet travels at a very high speed and makes a large impact on the glass plane when it strikes it. The glass is at rest and due to inertia the rest of the plane remains in rest while the location where bullet strikes shares a large velocity thus causing a hole.
8. When an athlete makes a jump by standing in one place, his body has to break the state of rest to come in motion and jump.
However, when an athlete comes running, his momentum is already gained, and state of body is in motion forward thus helping him take a better jump.
9. The water molecules are tended to persist at ease, due to the inertia that keeps them in state of rest. So, to get rid of the molecules, it is a good idea to break the inertia of cloth by shaking it. So, while shaking the wet cloth due to pressured force on the cloth, it would release the inertia water to run out of the wet cloth.
10. In case bus stops suddenly, luggage will continue to remain in state of motion due to inertia. Thus, luggage might fall off when bus comes to rest or starts suddenly. Rope is tied to avoid this.
11. Newton's third law of motion i.e. to every action there is an equal and opposite reaction. When the boatman pushes against the water the water exerts a reaction force and thus the boat moves forward. The stronger the force applied by the boatman on water is, the more reaction force is exerted on boat, thus pushing it forward.
12. Newton's third law of motion i.e. to every action there is an equal and opposite reaction. When the fireman holds a water hose from which water comes out at high force, an equal force is exerted by water on the hose. Thus, due to this reaction force it becomes tough for fireman to hold the pipe