P5 - Forces

Question 1

What is a vector quantity?

Answer 1

A quantity that has a magnitude and a direction.

Question 2

What is a scalar quantity?

Answer 2

A quantity with only a magnitude, no direction.

Question 3

What is the difference between mass and weight?

Answer 3

Mass is the amount of ‘stuff in an object’, whereas weight is the force acting on the object due to gravity.

Question 4

How do you work out the weight of an object?

Answer 4

Weight (N) = Mass (kg) x Gravitational Field Strength (N/kg)

Question 5

What is a free body diagram?

Answer 5

All the forces acting on an object.

Question 6

What is the resultant force?

Answer 6

The resultant force is the overall force of an object (consider horizontal and vertical forces seperatley)

Question 7

How do you find the work done of an object?

Answer 7

Work done (j) = Force (N) x Distance (m)

Question 8

What is the conversation rate of joules and newton metres?

Answer 8

1 joule = 1 Nm

Question 9

Describe the forces if an object is in equilibrium?

Answer 9

If all objects acting on an object equal a resultant force of 0, then the object is in equilibrium.

Question 10

How do you find the force of an object?

Answer 10

Force (N) = Spring constant (N/m) x Extension (m)

Question 11

How do you work out the elastic potential energy of an object?

Answer 11

Elastic potential energy (j) = ½ x spring constant (N/m) x extension² (m)

Question 12

What is displacement?

Answer 12

It measures distance and direction in a straight line from an object’s starting point to its finishing point.

Question 13

What is velocity?

Answer 13

Velocity is speed in a given direction.

Question 14

Define acceleration in terms of velocity and time.

Answer 14

Acceleration is the change in velocity in a certain amount of time.

Question 15

How do you work out the speed of an object?

Answer 15

Spped = distance/time

Question 16

How do you work out the acceleration of an object?

Answer 16

Acceleration (m/s²) = change in velocity (m/s) divided by time (s)

Question 17

What does the term ‘uniform acceleration’ mean?

Answer 17

A constant acceleration.

Question 18

What does the gradient represent for the following? a) distance-time graph b) velocity-time graph

Answer 18

a) speed b) acceleration

Question 19

What is terminal velocity?

Answer 19

When an object reaches maximum speed - it is caused when the frictional force is equal to the accelerating force.

Question 20

What are newton’s three laws of motion?

Answer 20

1. A force is needed to change a motion
2. Acceleration is proportional to the resultant force
3. When two objects interact, the forces they exert on eachother are equal or opposite.

Question 21

How do you work out a resultant force, without knowing the forces?

Answer 21

Resultant force (N) = Mass (kg) x Acceleration (m/s²)

Question 22

What is inertia?

Answer 22

Inertia is the tendency for motion to remain unchanged and to continue in the same state of motion.

Question 23

What is the stopping distance of a vehicle? How can it be calculated?

Answer 23

The distance it takes for a car to stop in an emergency.

Stopping distance = Thinking distance + Braking distance.

Question 24

State four things that can affect the braking distance of a vehicle?

Answer 24

Speed, weather or road surface, condition of tyres, condition of brakes.

Question 25

What is a typical reaction time for a person?

Answer 25

Between 0.2 and 0.9s.

Question 26

How do you work out the momentum of a collision?

Answer 26

Momentum (kg m/s) = mass (kg) x velocity (m/s)

Question 27

If the momentum is 4 before a collision, what is it after the collision?

Answer 27

It is also 4, because momentum is constant - it always stays the same.