physics

posted by .

A 6 kg box with initial speed 5 m/s slides across the floor and comes to a stop after 1.4 s.

a.What is the magnitude of the average net force on the box?

b.You put a 3 kg block in the box, so the total mass is now 9 kg, and you launch this heavier box with an initial speed of 5 m/s. How long does it take to stop?

  • physics -

    a = change in v/ change in t = -5/1.4 = -3.57 m/s^2
    so
    F = m a = 6(-3.57) = - 21.4 Newtons

    The friction force will be larger because proportional to the normal force (eight)
    F = -21.4 (9/6) = -32.1 Newtons friction force
    F = m a
    a = -32.1 / 9 = 3.57 m/s^2
    so same time, 1.4 seconds

    (the mass and the retarding force go u in the same proportion)

  • physics -

    Düsseldorf

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. physics

    The initial velocity of a 4.0-kg box is 11 m/s, due west. After the box slides 4.0 m horizontally, its speed is 1.5 m/s. Determine the magnitude and the direction of the non-conservative force acting on the box as it slides
  2. Physics

    A delivery person pulls a 35 kg box across the floor. The applied force exerted on the box is 122.5 N [38o above the horizontal]. The force of kinetic friction on the box has a magnitude of 55.0 N. The box starts from rest. Using the …
  3. physics

    A 15 kg box slides across the floor with an initial velocity of +7.6 m/s. It comes to a stop after sliding +14.8 m. How much friction was present?
  4. Physics (work and springs)

    A 4kg box is compressed 50cm on a spring (k=800 N/m) and then slides across a horizontal floor. If (u=0.4) between the box and the floor... A) how much work is done?
  5. Engineering Physics

    A 4kg box is compress 50 cm on a spring (k=100 N/m) and then slides across a horizontal floor. If (u=0.4) between the box and the floor 1) How much work is done by friction as the box comes to a stop?
  6. Physics

    A 16 kg box slides across the floor with an initial velocity of +7.8 m/s. It comes to a stop after sliding +14.6 m. How much friction was present?
  7. physics

    the initial velocity of a 4 kg box is 11 m/s, due west. after the box slides 4 m horizontally its speed is 1.5 m/s. determine the magnitude and the direction of the non conservative force acting on the box as it slides.
  8. physics

    a box of mass 5.7 kg slides across a floor and comes to a complete stop. if its initial speed was 10km/h and mu = 0.34 find the acceleration of the box
  9. Physics

    A 15 kg box is given an initial push so that it slides across the floor & comes to a stop. If the coefficient of friction is .30, A) Find the Ffr Fg=mg=Fg=15(9.8)=147N Ffr=mu(Fn)- Ffr=.3*147N=44.1N B)Find the acceleration. Hint: what …
  10. Physics

    A 15kg box is given an initial push so that it slides across the floor & comes to a stop. I the coefficient of friction is .30, a) find Ffr- Fg=mg - Fg=15kg(9.8N/kg)=147N Ffr=mu(Fn) - Ffr=.30(147N)=44.1 b) Find the acceleration of …

More Similar Questions