PHYSICS [3 Mark Question Answer]

Ways to reduce friction:

1. Providing ball bearings or wheels between the moving parts of the machine or vehicles reduces friction and allow smooth movement as rolling friction is less than sliding friction.
2. Oiling or lubricating (with graphite or grease) the moving parts of a machine reduces friction. Fine powder like talcum powder also works as a lubricant to reduce friction.
3. Polishing the rough surface reduces friction offered by it.
4. Streamlining (giving special shape to experience minimum drag) the bodies of aeroplanes, cars, boats, and ships help reduce drag (fluid friction) while travelling through air or water.

Force acting in one direction = 30 N
Force acting in opposite direction = 70 N
Resultant force = Difference between the magnitude of force
= 70 N – 30 N = 40 N
The car will move in the direction in which the force of 70 N is being applied. The resultant force of 40 N will act in the car.

Total forces acting to the left = 12 N + 25 N = 37 N
Force acting to the right = 35 N
The resultant force on the body = difference between the magnitude of the forces = 37 N – 35 N = 2 N
The object will move in the direction in which the force of 37 N is being applied, i.e., the resultant force of 2 N will act to the left.

The horses pull in the same direction. Therefore, the resultant force acting on the cart = sum of both the forces
= 500 N + 500 N = 1000 N
The resultant force of 1000 N will act in the same direction as the individual forces on the cart.

Difference between mass and weight Mass and weight mean completely different things in physics. The amount of matter that an object contains constitutes its mass. The gravitational force acting on this mass is called the weight of the object.
Mass of an object always remains the same, while the weight of the object varies when it is subjected to different gravitational forces. For example, the weight of an astronaut on the earth is six times her/his weight on the moon as the gravitational force of the earth is six times more than the gravitational force of the moon. But the body mass of the astronaut remains the same in both places

Ways by which friction can be increased are :

• Tires of all vehicles have grooved designs or treads to make their surface rough. The roughness of a surface increases friction and prevents a vehicle from slipping or skidding on a wet or muddy road.
• Spikes in the shoe soles used by players and athletes increase friction and they get a firm grip on the ground. The soles of footwear are also provided with grooved designs to increase friction and avoid slipping.
• The handles of motorbikes are covered with spiked rubber to provide a good grip and have better control in holding the handles.

Characteristics of the force of friction are :

• Friction opposes the direction of motion.
• It depends on the nature of the surface that is in contact. Rough surfaces offer a greater degree of friction as compared to smooth surfaces. More the roughness of a surface, the greater is the friction.
• Friction depends upon the weight of the object – greater is the weight of the object, greater is frictional force it faces.
• Friction is independent of the area of the surface in contact when the weight remains unchanged.