Conservation of momentum in a collision between particles can be understood from

A hockey player is moving northward and suddenly turns westward with the same speed to avoid an opponent. The force that acts on the player is

A body of mass 2 kg travels according to the law $$x(t)=p t+q t^2+r t^3$$ where, $$q=4 \mathrm{~ms}^{-2}, p=3 \mathrm{~ms}^{-1}$$ and $$r=5 \mathrm{~ms}^{-3}$$. The force acting on the body at $$t=2 \mathrm{~s}$$ is

A body with mass 5 kg is acted upon by a force $$\mathbf{F}=(-3 \hat{\mathbf{i}}+4 \hat{\mathbf{j}}) \mathrm{N}$$. If its initial velocity at $$t=0$$ is $$v=(6 \hat{\mathbf{i}}-12 \hat{\mathbf{j}}) \mathrm{ms}^{-1}$$, the time at which it will just have a velocity along the $$Y$$-axis is

A car of mass $$m$$ starts from rest and acquires a velocity along east, $$\mathbf{v}=v \hat{\mathbf{i}}(v>0)$$ in two seconds. Assuming the car moves with uniform acceleration, the force exerted on the car is