SHMD 239 KinesiologyUnit 5

Acceleration

Worksheet Questions & Answers

Question 1:

In the triathlon race, the time taken for the winner to complete the race was:

Work out the average velocity for the different components of the triathlon.

Distance Time

1600 m Swim 30 min

40 km Cycle 90 min

10 km Run 45 min

ANSWERS:

Swim:

Velocity = Displacement / Time

0m / 30 min

0km / 0.5 hr

0 km/hr

ANSWERS:

Cycle:

Velocity = Displacement / Time

40km / 90 min

0km / 1.5 hr

0 km/hr

ANSWERS:

Run:

Velocity = Displacement / Time

10km / 45 min

0.2km / 0.75 hr

0.27 km/hr

Question 2:

Dan & Gary were competing in a 800m race. Dan ran the first 400m of the race in 42 seconds and the second 400m in 58 seconds. Gary ran the first 400m in 52 seconds and the second 400m in 50 seconds.

Answer the following questions?

Who won the race?

What was the speed of each competitor?

What was the velocity of each competitor?

ANSWERS:

Who won the race?

Dan won the race.

Why?

Dan: 400m = 42 sec

400m = 58 sec

= 100 sec or 1.67 min

Gary: 400m = 52 sec

400m = 50 sec

= 102 sec or 1.7 min

ANSWERS:

What was the speed of each competitor?

Dan: Speed = Distance / Time

= 800m / 100 sec = 8 m/sec

Gary: Speed = Distance / Time

= 800m / 102 sec

= 7.84 m/sec

ANSWERS:

What was the velocity of each competitor?

Dan: Velocity = Displacement / Time

= 0m / 100 sec= 0 m/sec

Gary: Velocity = Displacement / Time

= 0m / 102 sec

= 0 m/sec

Question 3:

A swimmer covers the first 50m length of a 100m backstroke race at an average speed of 1.5m/s and the second length at an average speed of 1.2m/s.

What were the times for the first and second lengths, respectively?

What was the average speed for the whole race?

What was the average velocity for the whole race?

ANSWERS:

What were the times for the first and second lengths?

1st length: Speed = Distance / Time

1.5m/s = 50m / ? sec

Time= Distance / Speed

= 50m / 1.5m/s

= 33.33 s

ANSWERS:

What were the times for the first and second lengths?

2nd length: Speed = Distance / Time

1.2m/s = 50m / ? sec

Time= Distance / Speed

= 50m / 1.2m/s

= 41.67 s

ANSWERS:

What was the average speed for the whole race?

Speed = Distance / Time

= 100m/(33.33s + 41.67s) = 100m/75s

= 1.33 m/s

ANSWERS:

What was the average velocity for the whole race?

Velocity = Displacement / Time

= 0m/(33.33s + 41.67s) = 0m/75s

= 0 m/s

Acceleration

Is a vector quantity that is measured by the rate at which velocity changes

An object is accelerating if it is changing its velocity

Decelerating is the opposite of accelerating - slowing down

Acceleration = Change in Velocity / Time Taken

It can be worked out by finding:

(vf – vi)

t

Vf = final velocity

Vi = initial velocity

T = time interval

Units for acceleration = m/s²

QUESTION:

A softball player sprints from 1st base, to 2nd base. If her instantaneous horizontal velocity is 9.3m/s when she is 8m from 2nd base and 7.5m/s when she is 5m from 2nd base 0.4s later.

What is her acceleration over that 3m interval?

ANSWER:

Acceleration = (vf – vi)

t

= (7.5 – 9.3) m/s

0.4 s

= -1.8 m/s

0.4 s

= -4.5 m/s

End of Unit