The <u>speed</u> of the ride is
Speed = (distance covered) / (time to cover the distance)
Speed = (4,000 m) / (45 min)
Speed = <em>88.89 m/s</em>
Speed = <em>1.481 m/s</em>
Speed = <em>5.333 km/hr</em>
There's not enough information given in the question to calculate the velocity of the ride. For example ...
-- If the ride was completely in a straight line, then the velocity would be exactly equal to the speed.
-- If the rider went 2km from his house and then 2km back home again, his velocity for the whole ride would be zero.
We just don't know from the information given.
Answer: The horse is moving with a uniform acceleration
Explanation:
According to the described situation, we are dealing with a <u>constant acceleration</u> (also called <u>uniform acceleration</u>), since the horse's velocity is changingn by a constant rate.
Let's prove it:
Firstly we are told the horse follows a straight path. In addition we are given its velocity:
3 m/s, then 4 m/s and 5 m/s
Since acceleration 
is defined as the change of velocity in time we can calculate it:
This is the horse's constant acceleration
2.8 kg .............is the mass of a 1.2 N book.
1) The acceleration
Acceleration = Change in Speed / Time
Acceleration = (12 - 2) / 2
Acceleration = 10 / 2
Acceleration = 5m/s^2 (This is the unit for acceleration)
2) Initial momentum
Momentum = Mass x Velocity
Momentum = 1500 x 2
Momentum = 3000kg m/s (This is the unit for momentum)
3) Final momentum
Momentum = Mass x Velocity
Momentum = 1500 x 12
Momentum = 18000kg m/s
4) Change in momentum
Change in momentum = Final momentum - Initial momentum
Change in momentum = 18000 - 3000
Change in momentum = 15000kg m/s
5) Force
Force = Mass x Acceleration
Force = 1500 x 5
Force = 7500N (This is the unit for force)
Hope that helps :)
