please help?

Question

Pam has a mass of 35.2 kg and she is at rest on smooth, level, frictionless ice. Pam straps on a rocket pack. The rocket supplies a constant force for 19.4 m and Pam acquires a speed of 63.4 m/s. What is the magnitude of the force in N? And what is her final kinetic energy (in joules)?

Answer 1

Let's start with s = 1/2 at^2 + vo t + so. Since so and vo are zero, the equation is 19.4 = 1/2 at^2, or 38.8 = at^2.

Next we have v = at + vo, which becomes 63.4 = at.

That gives us two equations in two unknowns. (There are other equations that will do this, but I always forget those, and the fundamental equations will do the job.)

t = 63.4/a, and substituting, we have

38.8 = at^2 = 63.4^2/a = 4019.56/a

and a = 103.6 m/s/s

Now, F = ma = 35.2 x 103.6 = 3646.6N (ANSWER)

The kinetic energy is 1/2 mv^2 = 70744 joules (ANSWER)