p2 – forces and motion lesson 1: velocity and acceleration

Speed and Velocity What is meant by the terms:

Speed?

Velocity?

Keywords: Speed, Velocity, Acceleration, Keywords: Speed, Velocity, Acceleration,

is just how fast you are going with no regard to the direction.

Must have the direction specified as well as the speed.

Speed and Velocity Are these examples of speed or velocity?


30 mph Speed

30 km/h north

Velocity

15 cm/s Speed

10 m/s, 0600 Velocity

So:

Speed and velocity are both measured in the same units

and say how fast you are going.

Velocity though gives you the direction too.

Speed and Velocity You need to be able to calculate the speed of an

object. What do you need to know? (think about the units of speed).


How far something has travelled - distance

How long it took to travel that distance – time.

Remember: Speed is measured in mph, km/h, m/s, cm/s

Speed and Velocity So the formula to work out speed is:


Remember: Speed is measured in mph, km/h, m/s, cm/s

So the answer is in the units:

Distance = Speed Time

d

ts

Speed and Velocity So the formulas are:


d

ts

Speed = Distance Time

Time = Distance Speed

Distance = Speed x Time

Speed and Velocity

Lets use the formulas:


d

ts

1. A cat walks 20m in 35s. Find:

a. Its speedb. How long it takes to walk

100m1a. Speed = Distance = 20m Time 35s

Answer: 0.57 m/s (remember units)

Speed and Velocity

Lets use the formulas:


d

ts

1. A cat walks 20m in 35s. Find:

a. Its speedb. How long it takes to walk

100m1b. Time = Distance = 100m_

Speed 0.57m/s

Answer: 175s (remember units)

Speed and Velocity Lets use the formulas:


d

ts

To calculate velocity, we use the same formula.

All that we would need to add is the direction that the cat was walking.

Task

Answer the questions for you given number (6 questions).


AccelerationWhat is meant by the term:

Acceleration?


Is how quickly something is speeding up. (i.e. how quickly velocity is changing)

It is not the same as speed and velocity.

Acceleration So the formula to work out acceleration is:


Change in velocity = Acceleration Time Taken

v = change in velocity v

ta

Acceleration Units What are the units for acceleration?


Change in velocity = Acceleration Time Taken

Velocity is m/sTime is s

So: m/s s

Answer: m/s2

Acceleration Lets see if we can use the formula:


1. A bike accelerates steadily from 2m/s to 6m/s in 5.6s. Find the acceleration:

v

ta

v = 6m/s – 2m/s = 4m/sa = ?T = 5.6s

So: Acceleration = Velocity = 4m/s

Time Taken 5.6s

Answer: 0.71 m/s2

Questions


1. a. Find the speed of the mouse which hobbles 3.2m in 35s. b. Find how far it will get in 25 minutes.

2. A speed camera is setup in a 30mph (13.4 m/s) zone. It takes two photographs 0.5s apart. A car travels 6.3m between the two photographs. Is the car breaking the speed limit?

3. What is the acceleration of a coin flicked from rest to a speed of 14m/s in 0.4s?

0.09m/s137m

No (12.6m/s)

35m/s2

Task

Answer the questions for you given number (6 questions).


Are you now able to….

I still feel unsure. I need some more help to understand.

I feel ok. I need to do some more work to check my understanding.

I am happy and feel I understand and can explain the main points.


Using only the following materials you need to design and

make a run for a marble to travel form your desk to the

floor in the longest time.

Rules:

• You can only use paper and sticky tape.

• You can not touch the marble once it has been released.

• Your marble MUST reach the floor.

Marks:

• You will be ranked in time order.


Video

p2 – forces and motion lesson 1: velocity and acceleration

Documents

units of speed

speed timedtsspeed

examples of speed

speed camera

speed limit

velocity vtaacceleration

speed x timespeed

ms time