Pysics 11 problem. help please?

  • Thread starter Iceclover
  • Start date
  • #1
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Homework Statement



Pam has a mass of 40.0kg and she is at rest on a smooth level frictionless ice. pam straps on a rocket pack. the rocket pack supplies a constant force for 22.0m and pam acquires a speed of 62.0m/s

a)what is the magnitude of the force?
b)what is pams final kinetic energy

Homework Equations



a)F=mg
b)Ek=1/2mv^2



The Attempt at a Solution



a)
m=40.0kg
d=22.0m
v=62.0m/s
F=mg
F=(40.0)(9.8)
F=392N

b)
m=40.0
v=62.0
Ek=?
Ek=1/2mv^2
Ek=1/2(40.0)(62.0^2)
Ek=7.69x10^4J
 

Answers and Replies

  • #2
cristo
Staff Emeritus
Science Advisor
8,107
73

Homework Statement



Pam has a mass of 40.0kg and she is at rest on a smooth level frictionless ice. pam straps on a rocket pack. the rocket pack supplies a constant force for 22.0m and pam acquires a speed of 62.0m/s

a)what is the magnitude of the force?
b)what is pams final kinetic energy

Homework Equations



a)F=mg
b)Ek=1/2mv^2



The Attempt at a Solution



a)
m=40.0kg
d=22.0m
v=62.0m/s
F=mg
F=(40.0)(9.8)
F=392N
This is not the force you were asked for: this is the weight of the person. Try using the relevant kinematic equation to calculate the acceleration, then use newtons 2nd law to work out the force.
b)
m=40.0
v=62.0
Ek=?
Ek=1/2mv^2
Ek=1/2(40.0)(62.0^2)
Ek=7.69x10^4J
This looks fine
 
  • #3
59
0
how do i figure out the acceleration without the force?
 
  • #4
59
0
wow i definately did not do this right, i got 3480
 
  • #5
cristo
Staff Emeritus
Science Advisor
8,107
73
how do i figure out the acceleration without the force?
Using the kinematic equations [hint: the relevant one to use here is v2=u2+2as, where here v is the final velocity, u is the initial velocity, a is acceleration and s is the distance.]
 
  • #6
cristo
Staff Emeritus
Science Advisor
8,107
73
wow i definately did not do this right, i got 3480
I get 3495N
 
  • #7
59
0
i got 3520
 
  • #8
59
0
ok so if you put it into sig figs you would get 3.5x10^3
 
  • #9
cristo
Staff Emeritus
Science Advisor
8,107
73
ok so if you put it into sig figs you would get 3.5x10^3
Yes, if you're using 2sf.
 
  • #10
59
0
ok so thats right then?
 

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