Change of Momentum:
To calculate the change of momentum, we need to find the initial momentum and final momentum of the hockey ball. The change of momentum is the difference between these two values.

Initial Momentum:
The initial momentum of an object is given by the product of its mass and velocity. In this case, the mass of the hockey ball is 200g, which is equal to 0.2kg, and the initial velocity is 10 m/s. Therefore, the initial momentum is:

Initial Momentum = Mass × Velocity = 0.2 kg × 10 m/s = 2 kg⋅m/s

Final Momentum:
The final momentum of the hockey ball is given by the product of its mass and final velocity. In this case, the mass remains the same at 0.2kg, and the final velocity is 5 m/s. Therefore, the final momentum is:

Final Momentum = Mass × Velocity = 0.2 kg × 5 m/s = 1 kg⋅m/s

Change of Momentum:
The change of momentum is the difference between the final momentum and the initial momentum. Therefore, the change of momentum is:

Change of Momentum = Final Momentum - Initial Momentum
= 1 kg⋅m/s - 2 kg⋅m/s
= -1 kg⋅m/s

The negative sign indicates that the momentum of the hockey ball has decreased in the opposite direction to its initial motion.

Force Applied by the Hockey Stick:
The force applied by the hockey stick can be calculated using Newton's second law, which states that force is equal to the rate of change of momentum. Therefore, we can use the equation:

Force = Change of Momentum / Time

Since the time is not given in the problem, we cannot calculate the exact force applied by the hockey stick without this information. However, we can determine that the force applied will be negative since the change in momentum is negative. This means that the hockey stick applies a force opposite to the direction of the ball's motion, slowing it down.

It is important to note that the force applied by the hockey stick will depend on factors such as the duration of contact between the stick and the ball, the flexibility of the stick, and the angle at which the stick strikes the ball. Without these additional details, we cannot provide a precise calculation of the force.