The velocity-time graph of an object moving north-west is shown here. what is the instantaneous velocity of the object at time t=7.0 s

4.2 m/s

Explanation:

The velocity-time graph is piecewise linear. The acceleration in each of the three segments of the graph is uniform. The instant  lies between  and t = 6.0s 100 s, so the acceleration must be calculated using the slope of the middle segment.  

a =  

(9.6 -2.4)m/s

(10.0 -6.0)s

= 1.8 m/s2

The instantaneous velocity is to be found after the object accelerates over an interval T = (7.0 - 6.0) s = 1.0 s, starting from a velocity of 2.4 m/s,

So the velocity at t = 7.0 s is

v = u + aT = 2.4 m/s + (1.8 m/s2)(1.0 s) = 4.2 m/s

the displacement produced by the body.  

the amount of force subjected to the body.  

the angle between the direction of force and displacement