forces

Question 1

Definition of a force

Answer 1

Friction is the contact force that opposes or tends to oppose motion
between surfaces in contact.

Question 2

SI unit of force

Answer 2

Newton(N)

Question 3

Name the contact forces

Answer 3

• normal reaction
• friction
• tension

Question 4

name the non contact forces

Answer 4

• gravitational force
• electric force
• magnetic force

Question 5

Newton’s first law

Answer 5

Newton’s first law of motion states that every object will continue in its state of rest or uniform motion in a straight line unless a resultant force acts on it.

Question 6

Newton’s second law

Answer 6

Newton’s second law of motion stated that when a resultant force acts on an object of a constant mass, the object will accelerate in the direction of the resultant force. The product of the mass and acceleration of the object gives the resultant force. (F=ma)

Question 7

Newton’s third law of motion

Answer 7

Newton’s third law of motion states that for every action, there is an equal and opposite reaction.

Question 8

4 characteristics of forces

Answer 8

1. Forces always occur in pairs. the action force and the reaction force.
2. Action and reaction forces are equal in magnitude.
3. Action and reaction forces act in opposite directions.
4. Action and reaction forces act on different bodies.

Question 9

Definition of friction

Answer 9

Friction is the contact force that opposes or tends to oppose motion between surfaces in contact.

Question 10

How do wheels reduce negative effects of friction

Answer 10

The circular shape of wheels reduce the area of the contact surfaces. with less friction, a smaller force is needed to move a shopping trolley.

Question 11

How do ball bearings reduce the negative effects of friction

Answer 11

Spherical ball bearings work like wheels. They roll around and prevent moving surfaces in machines from rubbing against each other directly.

Question 12

How do lubricants reduce negative effects of friction

Answer 12

Lubricants and polished surfaces smooth over and remove surface irregularities, so engine surfaces in contact experience less friction when they move against each other.

Question 13

How do air cushions reduce negative effects of friction

Answer 13

A layer of air between surfaces reduces friction, so a hovercraft can travel faster.

Question 14

How do treads enhance positive effects of friction

Answer 14

Treads can channel water out from tires, which improves the tires’ grip on the road surface, and prevents vehicles from skidding.

Question 15

How do parachutes enhance positive effects of friction

Answer 15

The large air resistance created by the canopy of an open parachute slows down a descending parachutist, so that they may land safely.

Question 16

How do lubricants reduce negative effects of friction

Answer 16

Lubricants and polished surfaces smooth over and remove surface irregularities, so engine surfaces in contact experience less friction when they move against each other.

Question 17

How does chalk enhance positive effects of friction

Answer 17

Rock climbers apply chalk powder to their palms to absorb sweat, and hence improve their grip.