# Questions related to Kinematics

#### alexandria

Member reminded that separate problems should be given separate threads.
1. Homework Statement
so im sending my unit in for marking, and i collected a bunch of kinematic related questions that i've attempted to answer, but dont know if im on the right track. Any help would be appreciated. Thanks.
1.

2.

3.

4.

5.

2. Homework Equations
relevant equations are listed with each question

3. The Attempt at a Solution

1.
The truck travelled 14.0 km (South) in 15 min. The truck continued another 6 km at a slower pace over 10 min, and then stayed at this location for 5 min. The truck continued on at a constant speed for another 8 km towards the destination, taking 15 min for this portion of its journey.

2.
Displacement = 131 km (South)

Average velocity = total displacement / total time

Average velocity = 131 km (S) / 2.0 h

Average velocity = 65.5 km /h (south)

3.
a)

d = v x t

Time to cross river:

t = d / v

= 0.032 km / 2.5 km/h

= 0.0128 hrs

Walking distance:

d = (1.2 km/h) x (0.0128 hrs)

d = 0.01536 km = 15.36 m

Sandra will have to walk 15.36 m to reach the farmer’s market.

b)
Time it takes to cross the river:

t = d / v

t = 32.0 m (E) / 0.69 m/s (E)

t = 46 s

Time it takes to walk the riverbank:

t = d / v

t = 15.36 m / 0.72 m/s

t = 21 s

Walking to the farmer’s market will result in the shortest time for Sandra to reach her destination.

4.
Increase the launch angle above 45 degrees, to reduce the horizontal displacement. This way the water balloon will hit the target instead of passing it.

5.
is it because the supplies will be blown off course??

#### Attachments

• 18.3 KB Views: 255
• 20 KB Views: 257
Related Introductory Physics Homework Help News on Phys.org

#### andrewkirk

Homework Helper
Gold Member
The truck continued another 6 km at a slower pace over 10 min
Are you sure it 'continued' in the same direction? What does the fact that the North-South coordinate is reducing over this 10 minutes tell us?
The truck continued on at a constant speed for another 8 km towards the destination
Towards the destination? What do you mean by the destination? A place to deliver cabbages, or the home depot?

Homework Helper
Gold Member
2018 Award

#### alexandria

"Are you sure it 'continued' in the same direction? What does the fact that the North-South coordinate is reducing over this 10 minutes tell us?"
is the truck now travelling in an east-south direction?

#### andrewkirk

Homework Helper
Gold Member
is the truck now travelling in an east-south direction?
We are given no information about its East-West coordinates. Only the North-South coordinates are given. Hence we should assume that it is travelling only along a road that runs North-South.

#### alexandria

so was the truck travelling North initially, but then began to travel towards the south direction?

#### andrewkirk

Homework Helper
Gold Member
No, travelling South first, because the coordinate given is the km to the South. THen turns and travels North later.

#### haruspex

Homework Helper
Gold Member
2018 Award
so was the truck travelling North initially, but then began to travel towards the south direction?
Nearly right. That might not be what you intended to say.

#### alexandria

so is this how it goes:
The truck travelled 14.0 km (South) in 15 min. The truck then travelled another 6 km North at a slower pace over 10 min, staying at this location for 5 min. The truck continued on at a constant speed for another 8 km towards the destination, taking 15 min for this portion of its journey.

also am i right that the truck continues at a constant speed?

#### haruspex

Homework Helper
Gold Member
2018 Award
so is this how it goes:
The truck travelled 14.0 km (South) in 15 min. The truck then travelled another 6 km North at a slower pace over 10 min, staying at this location for 5 min. The truck continued on at a constant speed for another 8 km towards the destination, taking 15 min for this portion of its journey.

also am i right that the truck continues at a constant speed?
Yes, but as has already been suggested you should state the speeds.

#### alexandria

oh ok, but im following the example in my lesson, so in that context do you think my answer is valid.

#### Attachments

• 11.9 KB Views: 240

Homework Helper
Gold Member
2018 Award

#### alexandria

ok thank you for your help.

"Questions related to Kinematics"

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving