How to calculate the distance travelled in work and energy?

[red1312]

Homework Statement

A body of mass 8.0 kg is initially at rest on a horizontal frictionless surface. A
force of 18 N acts on it and accelerates it to a final velocity of 12 m/s. Calculate
(a) the distance travelled,
(b) the work done by the force,
(c) the final KE of the body,

Homework Equations

NONE

The Attempt at a Solution

(a): x=7.35
(b) W= 132.3 J
(c) KE= 48 J

 

[andrevdh]

How did you get at the answer for a?

 

[collinsmark]

It doesn't look right to me. How did you come about those answers?

 

[red1312]

Well that is the problem ,,, I just use g instead of a

 

[red1312]

Oh right to find a Can I use F=ma

 

[red1312]

x= 32 m
W= 576 J
KE = still 48 J

Am I right ??

 

[collinsmark]

x= 32 m
W= 576 J
KE = still 48 J

Am I right ??

The first two look somewhat promising (I'd be more definitive about it though if you showed your work).

The third one doesn't look so promising.

How did you come about your answers? (Hint: in the final answer, I think you forgot to square something.)

 

[gneill]

Homework Statement

A body of mass 8.0 kg is initially at rest on a horizontal frictionless surface. A
force of 18 N acts on it and accelerates it to a final velocity of 12 m/s. Calculate
(a) the distance travelled,
(b) the work done by the force,
(c) the final KE of the body,

Homework Equations

NONE

Now that can't be true! How are you doing any calculations?
What equations of motion and/or energy do you know?

The Attempt at a Solution

(a): x=7.35
(b) W= 132.3 J
(c) KE= 48 J

You need to show how you got your results. We can't just confirm results, we need to see your work. In that way we can help you to understand where your process is correct or incorrect.

 

[red1312]

Okey

(a) F=ma
18=8a
a=2.25
v^2=v0^2+2ax
x= 32m

(b) W=Fd
= 18(32)
= 576 J

(c) KE= 1/2 mv^2
= 8(144)/2
= 576 J

 

[gneill]

Okey

(a) F=ma
18=8a
a=2.25
v^2=v0^2+2ax
x= 32m

(b) W=Fd
= 18(32)
= 576 J

(c) KE= 1/2 mv^2
= 8(144)/2
= 576 J

Yes! Well done for each!

 

[red1312]

Thank you so much !