P2.2 - Forces

Question 0

What is the unit of force?

Answer 0

The unit of force is a Newton.

Question 1

What can forces do?

Answer 1

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

Question 2

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

Answer 2

They always exert equal and opposite forces on each other.

Question 3

What is the resultant force?

Answer 3

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

Question 4

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

Answer 4

The object stays at a constant velocity.

Question 5

How is resultant force calculated?

Answer 5

• The sum of the forces in the same direction.

- The difference of the forces in opposite directions.

Question 6

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

Answer 6

The bigger the resultant force, the greater the acceleration.

Question 7

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

Answer 7

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

Question 8

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

Answer 8

Resultant force (N) = mass (kg) x acceleration (ms^1)
F=ma

Question 9

Which forces oppose the driving force of a car?

Answer 9

Friction and air resistance.

Question 10

Give the two factors which affect stopping distance.

Answer 10

Thinking and braking distance.

Question 11

Give four factors that can increase the braking distance.

Answer 11

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

Question 12

Give two factors which can effect thinking distance.

Answer 12

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

- High speed.

Question 13

How is the braking force required effected by the car?

Answer 13

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

Question 14

What is the difference between mass and weight?

Answer 14

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

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

Question 15

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

Answer 15

The object accelerates at 10ms^-2.

Question 16

What is terminal velocity?

Answer 16

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

Question 17

How is weight calculated?

Answer 17

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

Question 18

How is the extension of an object measured?

Answer 18

The difference between the length and the original length.

Question 19

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

Answer 19

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

Question 20

What is the spring constant of a spring?

Answer 20

The force per unit extension needed to stretch it.

Question 21

What force is stored when an elastic object is stretched?

Answer 21

Elastic Potential Energy

Question 22

What is the equation of Hooke’s Law?

Answer 22

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

Question 23

Give four ways the fuel economy of vehicles be improved.

Answer 23

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

Question 24

What is an average speed camera?

Answer 24

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

Question 25

How do anti-skid surfaces work?

Answer 25

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