Physics Energy Question

Question

A 12 Kg object starts at rest on a horizontal surface. The object is pushed along the surface with a net force of 8.0 N. What is the speed of the object after it has traveled 5.0 m?

a) Solve using work and energy

b) Solve using kinematics and dynamics

Answer 1

Jiso

Using work and energy. Kinetic energy = Force applied x distance = Fs

1/2 mv² = Fs. m = 12, F = 8, s = 5. So v² = 2Fs/m = 2.8.5/12 = 6.67, so v = 2.58 m/s

Using kinematics and dynamics

F=ma, and v²=u²+2as.

F = 8, m=12, u=0 (initial speed). So a = F/m = 8/12, and v² =2as = 2 . (8/12). 5 = 80/12 = 6.67

So v = 2.58 m/s, agreeing with the first answer.

Mike