# P2.2 - Forces Flashcards

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0
Q

What is the unit of force?

A

The unit of force is a Newton.

1
Q

What can forces do?

A

Force can change the shape of an object or change its motion or its state of rest.

2
Q

When two objects interact what can we say about the forces acting?

A

They always exert equal and opposite forces on each other.

3
Q

What is the resultant force?

A

A single force that the same affect as all the forces acting on an object.

4
Q

What happens to an object if it’s resultant force is zero?

A

The object stays at a constant velocity.

5
Q

How is resultant force calculated?

A
• The sum of the forces in the same direction.

- The difference of the forces in opposite directions.

6
Q

How does the acceleration of an object depend on the size of the resultant force?

A

The bigger the resultant force, the greater the acceleration.

7
Q

What effect does the mass of an object have on its acceleration?

A

The greater the mass, the smaller the acceleration for a given force.

8
Q

How is resultant force on an object calculated from its mass and acceleration?

A
```Resultant force (N) = mass (kg) x acceleration (ms^1)
F=ma```
9
Q

Which forces oppose the driving force of a car?

A

Friction and air resistance.

10
Q

Give the two factors which affect stopping distance.

A

Thinking and braking distance.

11
Q

Give four factors that can increase the braking distance.

A
• Poor weather (ice, rain etc.)
• High speed.
• Poor brakes.
• Poor tyres.
12
Q

Give two factors which can effect thinking distance.

A
• Poor reaction time (caused by phone, alcohol, drugs etc.)

- High speed.

13
Q

How is the braking force required effected by the car?

A

The greater the speed, the more deceleration needed to stop the object.
The greater the mass, the greater the braking force needed.

14
Q

What is the difference between mass and weight?

A

The weight of an object is the force of gravity on it.

The mass of an object is the quantity of matter in it.

15
Q

What is the motion of a falling object only effected by gravity?

A

The object accelerates at 10ms^-2.

16
Q

What is terminal velocity?

A

The maximum velocity an object reaches when falling in a fluid.
The weight is equal to the drag force.

17
Q

How is weight calculated?

A

weight (N) = mass (kg) x gravitational field strength (Nkg^-1)
W=mg

18
Q

How is the extension of an object measured?

A

The difference between the length and the original length.

19
Q

How does the extension of a spring vary with the force applied?

A

The extension of the spring is directly proportional to the force up to the point of proportionality.

20
Q

What is the spring constant of a spring?

A

The force per unit extension needed to stretch it.

21
Q

What force is stored when an elastic object is stretched?

A

Elastic Potential Energy

22
Q

What is the equation of Hooke’s Law?

A
```force applied (N) = spring constant (Nm^-1) x extension (m)
F=ke```
23
Q

Give four ways the fuel economy of vehicles be improved.

A
• Reducing the speed.
• Fitting a wind deflector (for lorries.)
• Fully inflating the tyres.
• Removing excess weight.
24
Q

What is an average speed camera?

A

Linked pairs of cameras which record the vehicle’s average speed.

25
Q

How do anti-skid surfaces work?

A

The rougher surface increases friction meaning more force can be applied before the brakes lock.