Physics Design Practical

One of the forces that affect the tub from continuously moving is friction. Friction works in opposition with the movement of the object. The surface of the tub is rough and the surface of the floor is also rough, so the two surfaces catch and the tub slows down. One other force slowing the tub down is air resistance. Air resistance is when the face of the tub collides with the air particles and will slow the movement of the tub down.

A force is a push or a pull and is measured in newtons. The band pushes the tub, therefore it moves. When a force is applied to an object it can change three things about it. It can change the speed of an object, the direction of an object or the shape. In this experiment when force is applied to the tub, the speed will increase, till friction and air resistance is dominant over the force and it stops.

When the force pushes the tub it accelerates and the tub travels at a steady speed. The greater the force applied to the mass of the tub, the greater the acceleration. This is Newtons 2nd law of motion.

F = ma

Variables

Table 1: Defining Variables

Controlling Variables

Table 2: Variables and Method of Control

Apparatus

• An elastic band
• A 50g margarine tub
• A 100g weight
• A stool
• Flat surface (ie. floor)
• A Newton meter
• A meter ruler
• Chalk

Method

1. Place the stool on a flat surface and mark a line with chalk to keep the starting point the same
2. Attach the rubber band to the two front legs of the stool
3. From the start of the stool legs tape the ruler to the ground so it won’t move, but far enough away to not interrupt the path of the margarine tub
4. Next to the rubber band, set up the Newton meter
5. Place the 100g mass in the margarine tub then place the tub on the rubber band and stretch until the force applied according to the Newton meter in 2N
6. Record the distance the elastic band must be pulled back to reach this force and record it in table 3
7. Let go of the elastic band and allow the margarine tub to come to a complete stop before measuring the distance it has travelled (record in table 4)
8. Repeat steps 5-7, four times for each mass to find an average

Data Collection and Processing

Table 3: The distance the rubber band must be pulled back to reach the required force

Table 4: The distance travelled by the margarine tub at different forces