Answer:position function at time,t=r(t)=ti-tj+5t^2K+C
Speed at time,t=square root(2+25t^2)
Step-by-step explanation: Force= mass× acceleration =F=ma
a=f/m
Given: force=20N ,Mass=4kg
a=20/4=5m/s
a(t)=5K. Using integration
V(t)=5tK+C
Where C is constant of integration.
Given:v(0)=i-j
V(0)=5(0)+K
Zi-j=0+C integrating to get the position function gives:
r(t)=ti-tj+5t^2 K +C
C=0 because object started at origin
Speed is magnitude of velocity
V(t)=i-j+5t K
/v(t)/÷ squareroot(1^2+(-1)^2)+5t^2
Speed = squareroot (2+25t^2)
