Newton's Laws -- Resting hockey puck hit with a force

In summary, a hockey puck is hit with a force of 15.3 N and the frictional force slowing the puck down is 1.0 N. The puck will travel 108 m in 3.0 s.
  • #1

Homework Statement


A resting hockey puck is hit with a force of 15.3 N. The frictional force slowing the puck down is 1.0 N.
a) Find the net horizontal force acting on the puck while the stick is in contact with the puck.
b) If the puck leaves the stick with a velocity of 45 m/s, how far will the puck travel in 3.0 s?

Homework Equations


Fnet (h) = Fapplied + Ff
a = F/m
Δd = v1Δt + 1/2 aΔt2

The Attempt at a Solution


a) Fnet (h) = Fapplied + Ff

Fnet (h)= (15.3 N [forward]) + (1.0 N [backward ])

Fnet (h)= (15.3 N [forward]) + (-1.0 N [forward])

= 14.3 N [forward]

Fnet (h) = 14 N [forward]

c)m = 164 g = 0.164 kg

a = F/m

a = -1.0 N [forward] / 0.164 kg

a= -6.1 m/s2 [forward]

Δd = v1Δt + 1/2 aΔt2

Δd = (45 m/s) (3.0 s) + ½ (-6.1 m/s2) (3.0 s)2

Δd = 108 m (should I add a direction here, if yes then would it be 108 m [forward]?)

The puck will travel 108 m in 3.0 s.

Is this correct?
 
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  • #2
Your work looks correct to me. I don't think you need to include a direction for the distance traveled.
 
  • #3
Ok, thanks for verifying my answer :)
 
  • #4
In your answer to a), why did you round to 14N?
 
  • #5
I just thought I should round it to two sig-figs... is it more accurate to leave it as 14.3 N?
 
  • #6
Evangeline101 said:
I just thought I should round it to two sig-figs... is it more accurate to leave it as 14.3 N?
The given data were both quoted to one decimal place, so you are justified (here) in doing so in the answer. In more complicated algebraic relationships it is not quite that simple.
 
  • #7
So does that mean I should leave it at 14 N? or change it to 14.3 N?
 
  • #8
Evangeline101 said:
So does that mean I should leave it at 14 N? or change it to 14.3 N?
I would submit the answer as 14.3N.
 
  • #9
haruspex said:
I would submit the answer as 14.3N.

Okay, thanks for the help :)
 

1. How do Newton's Laws apply to a resting hockey puck hit with a force?

Newton's First Law, also known as the Law of Inertia, states that an object at rest will remain at rest unless acted upon by an external force. This means that the hockey puck will remain stationary until it is hit with a force.

Newton's Second Law, also known as the Law of Acceleration, states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This means that the greater the force applied to the hockey puck, the greater its acceleration will be.

Newton's Third Law, also known as the Law of Action and Reaction, states that for every action, there is an equal and opposite reaction. This means that when the hockey puck is hit with a force, it will exert an equal force in the opposite direction.

2. Why does a resting hockey puck move when hit with a force?

A resting hockey puck will only move when hit with a force because of Newton's First Law. Without an external force acting on it, the puck will remain at rest due to its inertia. When a force is applied, the puck's inertia is overcome and it begins to move.

3. How does the mass of the hockey puck affect its movement when hit with a force?

According to Newton's Second Law, the mass of an object has an inverse relationship with its acceleration. Therefore, the greater the mass of the hockey puck, the slower it will accelerate when hit with a force. This is why heavier pucks require more force to be hit the same distance as lighter pucks.

4. Can the direction of the force affect the movement of the hockey puck?

Yes, the direction of the force can affect the movement of the hockey puck. According to Newton's Second Law, the acceleration of an object is directly proportional to the net force acting on it. This means that the direction of the force can determine the direction of the puck's movement.

5. How do friction and air resistance play a role in the movement of a hockey puck hit with a force?

Friction and air resistance can both act as external forces on a hockey puck hit with a force. Friction between the puck and the surface it is on can slow down its movement, while air resistance can also slow it down by pushing against its motion. These forces must be taken into account when predicting the movement of the puck after being hit with a force.

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