Chapter 3: Forces and Motion

Question 1

What is the equation for Average Speed?

Answer 1

Average Speed = Distance Travelled (m) / Time Taken (s)

Question 2

What is the gradient on a Distance-Time Graph?

Answer 2

The Speed of the object.

Question 3

What is instantaneous speed?

Answer 3

The speed of an object over a short interval of time.

Question 4

How is the instantaneous speed found?

Answer 4

By drawing a tangent at the point of instantaneous speed and calculate its Gradient.

Question 5

What is the definition of Displacement and Velocity?

Answer 5

Displacement is the distance of an object from a fixed point in a given direction.

Velocity is the rate of change of displacement.

Question 6

What is the gradient on a displacement-time graph?

Answer 6

Velocity.

Question 7

What is the definition of acceleration, and how is it calculated?

Answer 7

Acceleration is the rate of change of Velocity, and is calculated by Change in Velocity / Time.

Question 8

What is the gradient and area on a velocity-time graph?

Answer 8

The Gradient of a Velocity-Time Graph represents the acceleration, and the Area represents the displacement.

Question 9

What are the 5 Equations of motion, and when are they used?

Answer 9

The 5 Equations of Motion are:
s = ut + ½ at²
v = u + at
v² = u² + 2as
s = (u+v) / 2 t
s = vt - ½ at²

They are used when an object has a constant acceleration.

Question 10

What is the definition of Thinking Distance and Breaking Distance?

Answer 10

Thinking Distance is the distance travelled from seeing a reason to stop to applying the breaks.

Breaking distance is the distance travelled from applying the breaks to the vehicle coming to a stop.

Question 11

How do you calculate the Stopping Distance?

Answer 11

Stopping Distance is equal to Thinking Distance + Breaking Distance.

Question 12

What is the equation that links Thinking Distance, Speed, and Reaction Time?

Answer 12

Thinking Distance = Speed x Reaction Time

Question 13

What Factors affect the thinking and breaking distance?

Answer 13

Factors affecting Thinking Distance:
Visibility, Driver Condition, Driver Reaction Time, amount of sleep.

Factors affecting Breaking Distance:
Road Conditions (icy, wet), Tyre Conditions, Break Conditions.

Question 14

What is the Acceleration of Freefall?

Answer 14

The Acceleration of Freefall is equal to 9.81ms-². Assuming that air resistance is negligible.

Question 15

What is a Projectile?

Answer 15

A Projectile is an object that is thrown or propelled on the surface of the Earth and is under the influence of gravity.

Question 16

What are the rules of Projectile Motion?

Answer 16

The rules of projectile motion include:

• The Vertical Velocity of the object changes due to the acceleration of freefall.
• The Vertical Distance and Time of Flight can be calculated using equations of motion (often by resolving vectors and finding components).
• The Horizontal Velocity of the object remains constant.

Question 17

How can you calculate the distance travelled by an object propelled off a cliff?

Answer 17

You can calculate the distance by first finding the time taken for the object to hit the floor using SUVAT in the vertical direction, then times the Horizontal Speed by Time to find the distance travelled.

Question 18

How can you find the actual velocity and angle of a projectile travelling in a curved motion?

Answer 18

You can find the actual velocity of the object by finding the Horizontal and Vertical Components of Velocity and using Pythagoras to calculate its magnitude, and calculate its angle using Tan^-1 (Vertical Velocity / Horizontal Velocity).

Question 19

How can you calculate the Time Taken, Distance Travelled, highest point etc. for a Projectile fired upwards at an angle?

Answer 19

You can resolve the Vertical and Horizontal Components of Velocity, and use SUVAT to calculate missing values. Acceleration would be -9.81ms¯² due to gravity acting downwards.