P5 - Speed, Velocity & Combining Velocities and Force

Question 1

What do you need to measure the speed of an object?

Answer 1

To measure the speed of an object, you only need to measure how fast it is going, the direction is not important.

Question 2

Why is velocity more useful?

Answer 2

Velocity is more useful measurement of motion, because it describes both the speed and direction.
E.g. velocity = 30 mph Due north.

Question 3

What is a scalar quantity?

Answer 3

A scalar quantity is one that has only a number.

Question 4

What is a vector quantity?

Answer 4

A vector quantity has both direction as well as a numerical value.

Question 5

What are some examples of scalar quantities?

Answer 5

• Mass
• Speed
• Temperature
• Length
• Time

Question 6

What are some examples of vector quantities?

Answer 6

• Velocity
• Force
• Displacement
• Acceleration
• Momentum

Question 7

What is relative speed?

Answer 7

• How fast an object is moving relative to something else.

Question 8

How do you find the resultant velocity of two objects moving in different directions?

Answer 8

• If the velocities are moving in different directions than you take them away. E.g. A plane is travelling east, at 120 km/h, however there is a stream of air moving west at 20 km/h, what is the resultant velocity?
Answer: 120-20 = 100 km/h resultant velocity.

Question 9

How do find the resultant velocity of two objects moving in the same direction?

Answer 9

• For the same direction you just add the two velocities together.

Question 10

What do the different parts of S.U.V.A.T stand for?

Answer 10

• S = Displacement/Distance
• U = Initial Velocity
• V = Final Velocity
• T = Time
• A = Acceleration

Question 11

What are the suvat equations for distance?

Answer 11

• S = ( ( U + V ) / 2 ) T
• S = UT+½AT²
You need to be able to re-arrange these equations to find many other values.

Question 12

What are the suvat equations for velocity?

Answer 12

• V = U + AT
• V² = U²+2AS
You need to be able to re-arrange these equations to find many other values.

Question 13

What are some steps that you can take to find out what equation you wish to choose?

Answer 13

• Write down which three things you already know.
• Write down which of the other things you want to find out.
• Choose an equation which contains all of the things you have values for.
• Place the numbers in & carry out the maths.