Grade 11 physics

  • Thread starter Shaley
  • Start date
  • #1
12
0
PARTS C AND D ARE WHAT I'M HAVING TROUBLE WITH.

a tobaggan of mass 20kg is dragged horizontally across snow by someone who exerts a force of 45N. the tobaggan travels 8m under the action of the force and has a final speed of 2.6 m/s.
a)calculate the actual kinetic energy of the tobaggan based on its speed

Ek=1/2mv^2
=1/2(20)(2.6)
=67.6J

b)Calculate the amount of work actually done on the tobaggan by the applied force

W=F X d
=450X8
=3600J

c)From your answers to parts a and b, calculate the amount of thermal energy generated.

Ethermal=Ekinetic + Epotential
I know that potential =3600J from b (the actual work done), but what's the potential - would it be a's answer of 67.6?

d)Explain how this thermal energy was generated and state one effect it might have.

I think that it was generated by the friction caused between the tobagganand the snow, which the tobagan was being dragged.the effect is the the friction would cause a transfer of kinetic energy into the snow molecules. This increased vibration of snow molecules will cause and increase in the total energy, or thermal energy, which will cause the snow to melt. IS THIS RIGHT? THANKYOU.
 

Answers and Replies

  • #2
PhanthomJay
Science Advisor
Homework Helper
Gold Member
7,170
509
PARTS C AND D ARE WHAT I'M HAVING TROUBLE WITH.

a tobaggan of mass 20kg is dragged horizontally across snow by someone who exerts a force of 45N. the tobaggan travels 8m under the action of the force and has a final speed of 2.6 m/s.
a)calculate the actual kinetic energy of the tobaggan based on its speed

Ek=1/2mv^2
=1/2(20)(2.6)
=67.6J

b)Calculate the amount of work actually done on the tobaggan by the applied force

W=F X d
=450X8
=3600J
that's 45 x 8 = 360 J, typo error
c)From your answers to parts a and b, calculate the amount of thermal energy generated.

Ethermal=Ekinetic + Epotential
this equation is not correct; thermal energy is often just the heat energy generated by the work done by friction
I know that potential =3600J from b (the actual work done), but what's the potential - would it be a's answer of 67.6?
I think you are misunserstanding the concept of potential energy. Potential energy is generally associated witht the ability of gravity or spring forces to do work. 67.6 is the kinetic energy (of motion).
d)Explain how this thermal energy was generated and state one effect it might have.

I think that it was generated by the friction caused between the tobagganand the snow, which the tobagan was being dragged.the effect is the the friction would cause a transfer of kinetic energy into the snow molecules. This increased vibration of snow molecules will cause and increase in the total energy, or thermal energy, which will cause the snow to melt. IS THIS RIGHT? THANKYOU.
That's not quite correct; I wouldn't use the term kinetic energy, just say energy; and total energy of a system cannot either increase or decrease. The thermal energy was generated by ________? To calculate it, are you familiar with the work-energy or conservation of energy principles?
 
Last edited:

Related Threads on Grade 11 physics

  • Last Post
Replies
4
Views
1K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
11
Views
10K
  • Last Post
Replies
4
Views
3K
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
4
Views
5K
  • Last Post
Replies
2
Views
24K
  • Last Post
Replies
8
Views
3K
  • Last Post
Replies
8
Views
5K
Top