P2.1 - Motion

Question 1

What is speed?

Answer 1

The speed of a body (object) is the rate at which it covers distance.

Question 2

What are the two equations linking distance, speed, and time for uniform motion?

Answer 2

• Distance travelled (m) = Speed (m/s) x Time (s)
• Average Speed (m/s) = Total Distance (m) / Total
  time (s)

Question 3

What is the difference between uniform speed and non-uniform speed?

Answer 3

1. Uniform speed The speed stays constant for the whole journey. Speed calculated from distance and time is a single value
2. Non-Uniform The speed changes and is not the same during the journey. Speed calculated from (total) distance and (total) time is an average

Question 4

How many metres are in one kilometre?
How many metres are in one mile?
How many seconds are there in one hour?

Answer 4

• 1000m/km
• 1609m/mile
• 3600s/hour

Question 5

How do light gates work and why are they better than stopwatches?

Answer 5

• When you use a stopwatch there is a reaction
  time that affects the accuracy and precision of
  your measurement.
• A timer starts and stops when an object
  interrupts a light beam.

Question 6

How can you use ultrasound (high frequency sound waves) to measure distance?

Answer 6

• Measures the time taken for a pulse to travel and
  back.
• Uses this time halved and the speed of the pulse
  to work out the distance.

Question 7

What’s the difference between vector and scalar variables?

Answer 7

• Scalers only have magnitude.

- Vectors have both a magnitude and a direction

Question 8

How are vectors represented?

Answer 8

Vectors are represented by arrows…pointing in a given direction… with a given size.

Question 9

What is the difference between distance and displacement?

Answer 9

• Distance - The length of the path travelled from A
  to B - Scalar
• Displacement - The length of the shortest distance
  between two points - Vector

Question 10

What are the thee rules with adding vectors?

Answer 10

• If they act in the same direction, you add them.
• If they are in opposite directions, you subtract
  them.
• You can only add/subtract vectors that either
  act up and down or left and right.

Question 11

How do you find the relative velocity of two bodies?

Answer 11

Take the difference between the two bodies - Crucial to take into consideration the direction - Not the same idea as adding vectors.

Question 12

Define acceleration.

Answer 12

Acceleration is the rate of change of velocity of a body.

Question 13

How do you know if a body is accelerating?

Answer 13

If the speed and/or direction of motion change, the body is accelerating.

Question 14

What is the equation linking to acceleration?

Answer 14

acceleration (m/s2) = (final velocity- initial velocity(m/s)) / t (s)

Question 15

What is a distance time graph and what does its gradient show?

Answer 15

• A distance-time graph shows how the distance
  of an object changes with time.
• The gradient of a line on a distance-time graph is
  equal to speed.

Question 16

What is a velocity-time graph and what does its gradient show?

Answer 16

• Velocity-time graphs shows how the velocity of an object changes with time.
• They describe the acceleration of an object.
• The gradient of a line on a velocity-time graph is
  equal to acceleration.

Question 17

How do you calculate displacement with a velocity time graph?

Answer 17

The area under a line on a velocity-time graph is equal to the displacement.

Question 18

What is an equation of motion?

Answer 18

An equation of motion is an equation that links velocities, displacement, acceleration and time for bodies that have a constant acceleration.

Question 19

What is THE EQUATION of motion?

Answer 19

v2-u2=2as

Question 20

What is kinetic energy?

Answer 20

Kinetic energy is the energy of a body owing to its velocity.

Question 21

What is the equation linking to kinetic energy?

Answer 21

KE (J) = 1/2 x m(kg) x v2 (m2s2)