Question

A uniform force of 30N acts on a mass 2.5kg initially at rest for 5seconds then it withdrawn and a retarding force F now acted on the mass in the direction of the motion to reduce its velocity to 12 m/s.( calculate the momentum of mass before the retarding force starts to cut and the momentum of mass when its velocity is 12m/s if the retarding force acted for 7seconds,calculate its magnitude

Answer 1

Momentum before retarding force
Momentum =impulse =product of mass and velocity
M = Ft = mv
Using force and time
M = ft
= 30N × 5sec
= 150Ns

Momentum of mass when it's velocity is at 12m/s

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Answer 2

A force of 9.0N is applied to a body at rest on a smooth horizontal surface.
If the body has a mass of 18.0kg and it moves in the direction of the force, find the work done in.
a. The first four second. b. The fourth second ? Pls I need answers to this question pls