Newtons first and second law. What are the components of the force and what is its magintude.?

Question

To model a spacecraft, a toy engine is securely fastened to a large puck, which can glide with negligible friction over a horizontal furface, taken as teh xy plane. The 7.0kg puck has a velocity of 2.00i m/s at one instant. Eight seconds later, its velocity is to be (5.00i + 7.00j)m/s. Assuming the rocket engine exerts a constant total horizontal force, find the components of the force. Find its magniutde.

Answer 1

F = m a

= m (V2-V1) / t

= 7 / 8 * ( 3 i + 7 j) N

In SI (System International) force is measured in Newtons.
the answer is in N since all other units are in SI too.

Answer 2

Δv/Δt = (3.00i + 7.00j)/8 m/s/s
Fi = 7*3/8 dynes
Fj = 7*7/8 dynes
F = (7/8)sqrt(3^2 + 7^2)