Lesson 7: Speed/ Velocity/ Acceleration

Question 1

Is “speed” a scalar or vector quanitity?

Answer 1

• Scalar
• Has a magnitude, does not involve direction.

Question 2

True or False

The speed of a moving object rarely changes - it remains constant.

Answer 2

• False!!
• The speed of a moving object is rarely constant. When people walk,
  run or travel in a car their speed is constantly changing.

Question 3

What 4 main factors does the speed someone can walk, run or cycle depend on?

Answer 3

1.) Age
2.) Terrain
3.) Fitness
4.) Distance travelled.

Question 4

What is the APPROXIMATE value for walking speed?

Answer 4

walking ̴1.5 m/s

Question 5

What is the APPROXIMATE value for running speed?

Answer 5

running ̴3 m/s

Question 6

What is the APPROXIMATE value for cycling speed?

Answer 6

cycling ̴6 m/s.

Question 7

What is the APPROXIMATE speed of a car on a main road?

Answer 7

˜ 13m/s

Question 8

What is the APPROXIMATE speed of a fast train in the UK?

Answer 8

˜ 50m/s

Question 9

What is the APPROXIMATE speed of a cruising aeroplane?

Answer 9

˜ 250m/s

Question 10

It is not only moving objects that have varying speed. What other 2 speeds are varying?

Hint Hint think weather.

Answer 10

• The speed of sound
  AND
• The speed of wind
  ALSO VARY

Question 11

What is the typical value for the speed of sound in air?

Answer 11

330m/s

Question 12

What is distance? Is it a scalar or vector quantity?

Answer 12

• Distance is how far an object moves.
• Distance is a scalar quantity (as distance does not involve direction.)

Question 13

What is displacement?

Answer 13

• The distance an object moves (measured as a straight line from the start point to the finish point.)
  AND
• The direction of that straight line.

Question 14

Is displacement a scalar or vector quantity?

Answer 14

• Displacement is a vector quantity.

Question 15

What is velocity? Is velocity a scalar or vector quantity?

Answer 15

• The velocity of an object is its speed in a given direction.
• Velocity is a vector quantity.

Question 16

Why does an object moving in a circle have a constant speed but a changing velocity?

Answer 16

• As car moves around circle, the car changes direction.
• So, the velocity of the car always changes.

POINT: this also applies to when cars go around a corner as that is part of a circle (given that they are travelling at a constant speed.)

Question 17

When can the distance travelled by an object be represented by a distance-time graph?

Answer 17

• If the object moves along a straight line

Question 18

How can the average acceleration of an object be calculated?

Answer 18

acceleration = change in velocity/ time taken

Question 19

What is a decelerating object?

Answer 19

• A decelerating object is an object that slows down.

Question 20

How can the acceleration of an object be calculated using a velocity- time graph?

Answer 20

• Acceleration of object can be calculated from GRADIENT of velocity- time graph.

Question 21

How do you calculate the distance- travelled (displacement) from a velocity- time graph?

What METHOD does the SPEC want you to use??

Answer 21

• Area under graph
• Count how many COMPLETE or NEARLY complete squares there are under the graph.
• From the squares left (that aren’t complete/ nearly complete) approximate what the squares would add up to in total.
• Multiply the total number of squares by the area of each square.

Question 22

If an object is accelerating at a CONSTANT rate, what equation do we use to calculate the acceleration of the object.

Answer 22

v²- u² = 2as
v = final velocity
u = initial velocity
a = acceleration
s = distance

Question 23

What acceleration do objects falling freely under gravity near the Earth’s surface have?

Answer 23

9.8 m/s²

Question 24

What is the motion of an object falling through a fluid like?

Answer 24

• Object falling through fluid will initially accelerate due to the force of gravity.
• Eventually, the resultant force will be 0 and the object will move at its terminal velocity.