what is required to cause a body of mass 500g to accelerate uniformly from rest across a smooth horizontal surface so that it will cover a distance of 20 tometre in 4 seconds .​

A constant force of 1.25N

Explanation:

This is a kinematics problem.

First find acceleration,

then use F = ma to find force.

Given:

mass = .5kg

delta x = 20m

t = 4s

a = ?

Friction = 0

From the kinematics equations:

delta x = Vi + (1/2)at^2

Plug in terms that are given:

20m = 0 + (1/2)a(4^2)

(2*20m)/(16s^2) = a

40m/(16s^2)= 2.5m/s^2

Now use F = ma to find force exerted on object.

F = (0.5kg)*(2.5m/s^2)

F = 1.25N