2. How to calculate speed?
• Speed is a measure of how fast something is moving. It is the distance
moved per second or per hour.
• The unit of speed is metres per second (m/s) or kilometres per hour
(km/h).
• Speed = distance
time
12. Q4.2
• 1. timing gates are more accurate than using a stopwatch because the
measurement is taken exactly when the light beam broken. Using
stopwatch is less accurate because reaction time mean there is delay
in taking measurement.
• 2. it is important fir timing over short period of time because a delay
from reaction time would have a greater effect on the results.
• 3. Kyra. More significant
• 4. less than 0.2 s. If the sprinters leaves the block less than 0.2 s after
the gun, it is unlikely that they are reacting to the sound and have
false started.
21. Discuss Answers
• 1. Section E . Because it is the steepest.
• 2. a : Amira
• b. David stopped. Because a section of his graph where the distance
does not change.
• c. David
• d. Amira
• e. average speed = total distance/total time = 4500m/15 minutes =
4500m/900s = 5m/s
• 3. C : 1400m/13 min = 1400m/780 s = 1.8 m/s
• E: 2100m/10 min = 2100m/600s =3.5 m/s
22. Acceleration and speed-time graphs
• Calculating acceleration
• To calculate acceleration you need to know:
• The speed at the start
• The speed at the end
• The time it took for the speed to change
Acceleration = change in speed
time
Or
Acceleration = final speed - starting speed
time
23.
24.
25.
26.
27.
28.
29. Answers:
• 1. Speed is the distance travelled in a given time, Acceleration and
deceleration are how speed is changing over time. Acceleration is
when the speed is increasing and deceleration is when it is
decreasing.
• 2. ‘acceleration’, ‘horizontal’, ‘is not’
• 3. Acceleration of the ball = 25m/s - 0 m/s /0.05 s = 25/0.05 = 500m/s
4. Deceleration
