tarikan dan geseran = 拉力与摩擦力

Soalan pertama meminta aktiviti yang melibatkan tarikan, iaitu menggerakkan objek mendekati badan. Soalan kedua meminta cara mengurangkan geseran. Pelincir seperti minyak mengurangkan geseran, manakala bunga tapak kasut, sarung tangan dan alas anti-gelincir menambah geseran.

Contoh: Membuka laci ialah tarikan kerana laci bergerak ke arah badan.

Awas: Bunga pada permukaan menambah geseran, bukan mengurangkannya.

pull and friction = 拉力与摩擦力

The first question asks for an activity involving a pull, which moves an object towards the body. The second asks for a way to reduce friction. A lubricant such as oil reduces friction, while shoe patterns, gloves and non-slip mats increase friction.

Example: Opening a drawer is a pull because the drawer moves towards the body.

Watch out: A pattern on a surface increases friction, it does not reduce it.

menambah geseran dan tekanan udara = 增加摩擦力与气压

Balutan bercorak pada pemegang raket menambah geseran supaya raket tidak tergelincir dari tangan. Bagi kotak minuman yang kemek, tekanan udara di dalam kotak menjadi rendah. Udara perlu dibiarkan masuk supaya tekanan di dalam kembali sama dan minuman dapat disedut.

Contoh: Pemain badminton mahu raket digenggam kuat semasa memukul bulu tangkis.

Awas: Memicit kotak dengan kuat akan memercikkan minuman, bukan menyelesaikan masalah.

more friction and air pressure = 增加摩擦力与气压

Patterned grip tape on a racket handle increases friction so the racket does not slip from the hand. For a dented drink box, the air pressure inside the box has become low. Air must be let in so that the pressure inside becomes equal again and the drink can be sucked up.

Example: A badminton player wants a firm grip on the racket when hitting the shuttlecock.

Watch out: Squeezing the box hard will squirt the drink, it does not solve the problem.

tolakan dan tarikan = 推力与拉力

Tolakan menggerakkan objek menjauhi badan, manakala tarikan menggerakkan objek mendekati badan. Apabila menggulung tali layang-layang, tali ditarik ke arah badan. Apabila menolak kereta sorong bayi, kereta bergerak menjauhi badan. Kenal pasti arah gerakan objek.

Contoh: Menarik baldi air dari perigi menggunakan tali ialah tarikan.

Awas: Lihat arah objek bergerak berbanding badan.

push and pull = 推力与拉力

A push moves an object away from the body, while a pull moves an object towards the body. When reeling in a kite string, the string is pulled towards the body. When pushing a baby stroller, the stroller moves away from the body. Identify the direction the object moves.

Example: Lifting a bucket of water out of a well with a rope is a pull.

Watch out: Look at the direction the object moves compared with the body.

menyelesaikan masalah geseran = 解决摩擦力的问题

Jika masalahnya ialah tergelincir, kita perlu menambah geseran supaya kaki dapat mencengkam permukaan. Jika masalahnya ialah pergerakan yang terlalu sukar, kita perlu mengurangkan geseran. Rantai basikal yang berkarat menghasilkan geseran yang besar, jadi geseran perlu dikurangkan.

Contoh: Kasut sukan bertapak getah membantu pelari tidak tergelincir di trek basah.

Awas: Tentukan dahulu sama ada masalahnya tergelincir atau sukar bergerak.

solving friction problems = 解决摩擦力的问题

If the problem is slipping, we need to increase friction so the feet can grip the surface. If the problem is movement that is too hard, we need to reduce friction. A rusty bicycle chain produces large friction, so friction must be reduced.

Example: Sports shoes with rubber soles help runners not to slip on a wet track.

Watch out: First decide whether the problem is slipping or moving with difficulty.

daya dan kesannya = 力与力的效应

Menolak pintu kaca menjauhi badan ialah tolakan, dan mengangkat baldi dengan pemegangnya ialah tarikan. Semasa bermain badminton, bulu tangkis yang datang dipukul balik, jadi arahnya berubah. Pukulan yang kuat juga menjadikan bulu tangkis lebih laju, jadi lajunya berubah.

Contoh: Bola yang ditendang ke arah lain menunjukkan perubahan arah.

Awas: Satu daya boleh menghasilkan lebih daripada satu kesan.

forces and their effects = 力与力的效应

Pushing a glass door away from the body is a push, and lifting a bucket by its handle is a pull. In badminton, the incoming shuttlecock is hit back, so its direction changes. A strong hit also makes the shuttlecock faster, so its speed changes.

Example: A ball kicked another way shows a change of direction.

Watch out: One force can produce more than one effect.

pelincir = 润滑剂

Bunyi berdecit pada rantai basikal disebabkan oleh geseran antara bahagian logam. Menyapu minyak pelincir pada rantai mengurangkan geseran. Apabila geseran berkurang, bahagian logam bergerak dengan lancar, bunyi berkurang dan rantai tidak cepat haus.

Contoh: Engsel pintu yang berbunyi menjadi senyap selepas disapu minyak.

Awas: Terangkan bagaimana cara itu mengurangkan geseran.

lubricant = 润滑剂

The squeaking of a bicycle chain is caused by friction between metal parts. Applying lubricating oil to the chain reduces friction. When friction is reduced, the metal parts move smoothly, the noise is reduced and the chain does not wear out quickly.

Example: A squeaky door hinge becomes quiet after it is oiled.

Watch out: Explain how the method reduces friction.

permukaan dan geseran = 表面与摩擦力

Hanya jenis permukaan yang berbeza dalam eksperimen ini. Jubin paling licin, jadi paling mudah ditolak. Pasir paling kasar, jadi paling sukar ditolak. Oleh itu faktor yang mempengaruhi geseran ialah jenis permukaan, dan semakin kasar permukaan, semakin besar geseran.

Contoh: Menolak troli di atas jalan berbatu lebih sukar daripada di atas lantai pasar raya.

Awas: Kereta mainan yang sama digunakan, jadi jisim tidak berubah.

surface and friction = 表面与摩擦力

Only the type of surface differs in this experiment. The tiles are the smoothest, so the car is easiest to push. The sand is the roughest, so it is hardest to push. So the factor affecting friction is the type of surface, and the rougher the surface, the greater the friction.

Example: Pushing a trolley on a stony road is harder than on a supermarket floor.

Watch out: The same toy car is used, so the mass does not change.

mereka bentuk radas = 设计装置

Gunakan prinsip tekanan udara. Masukkan hujung hos ke dalam air di dasar botol dan hujung lagi ke dalam cawan. Tutup mulut botol dengan plastisin supaya udara tidak keluar, kemudian cucuk penyedut minuman pada plastisin. Tolak udara masuk menggunakan picagari supaya tekanan udara di dalam botol naik dan menolak air keluar melalui hos.

Contoh: Meniup udara ke dalam botol yang tertutup rapat menolak air keluar melalui hos.

Awas: Plastisin mesti menutup botol dengan rapat, jika tidak udara akan terlepas.

designing a set-up = 设计装置

Use the air pressure principle. Put one end of the hose into the water at the bottom of the bottle and the other end into the cup. Seal the bottle mouth with plasticine so no air escapes, then push a straw through the plasticine. Pump air in with the syringe so the air pressure inside the bottle rises and pushes the water out through the hose.

Example: Blowing air into a tightly sealed bottle pushes water out through a hose.

Watch out: The plasticine must seal the bottle tightly, or the air will escape.