Physics help.

Question

What force is needed to accelerate a 1300 kg car from rest to 20 m/s in 80 m?

Answer 1

 

Hey Sierra -- ave speed 10m/s travels 80m in 8 sec ... accel is 20/8 = 2.5 m/s/s ...

F=ma ... 1300kg(2.5m/s/s) = 2600N + 650N ~ 3.3kN ... Best wishes :)

Answer 2

The work-energy theorem states that the work done by non-conservative forces equals the change of the object's kinetic energy:

 

W = ΔKE

 

Now use the definitions of work and KE:

 

W = F Δx ,  ΔKE = KE_f - KE_i = ½m(v_f²-v_i²)

 

so that

 

F Δx = ½m(v_f²-v_i²)

 

F = ½(1300 kg) ((20m/s)²-0)/(80m) = 3,300 N

 

(I'm assuming 2 significant digits, though it could be just 1.)