Propulsive force and force at interface

In summary: For a) the horzontal force is directed to the right.For b) the force at the interface is directed to the left.
  • #1
cuj93
11
0

Homework Statement


Two blocks, one of mass 6 kg and the other of mass 2 kg, are placed in contact on a horizontal table, and a constant horizontal force is applied to the 6 kg mass. There is a constant frictional force of 18 N between the 6 kg mass and the table, but no frictional force between the 2 kg mass and the table. the blocks accelerate at 3 m/s2.
a. what is the propulsive force applied to the 6 kg mass?
b. what is the force at the interface between the two blocks?

Homework Equations


F=ma

The Attempt at a Solution


I honestly have no idea where to start I have read the book and looked at my notes and I am not sure where to start.
Fnet=ma
fnet= F-18[/B]
 
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  • #2
Start by drawing a large diagram on which you mark everything relevant. Examine it closely, looking for inspiration.

Post it here.
 
  • #3
upload_2014-10-16_3-11-25.png
 
  • #4
Now you can see what is going on!

Apply your Fnet = ma formula to the situation.
 
  • #5
Fnet=mneta
F-18=mneta
F-18=(6+2)(3)
F-18=24
F=42N
 
  • #6
is this correct?
 
  • #7
That looks right.

Next, what force must be being applied to the 2kg body to cause it to be accelerating at this rate? (Remember, if you don't apply sufficient force to it it won't accelerate at this rate, and if you were to apply more than the required force it will accelerate faster.)
 
  • #8
Will that force be the force at the interface. Since 2 kg mass experiences no friction
Fnet=ma
Fnet=2(3)
F=6N
 
  • #9
Will that force be the force at the interface. Since 2 kg mass experiences no friction
Fnet=ma
Fnet=2(3)
F=6N
Yes that force can only come from the bigger mass pushing on that leading body.
 
  • #10
So a) what is the propulsive force applied to the 6kg mass? 42N
and b) what is the force at the interface between the two blocks? 6N
 
  • #11
It's always a good idea to associate a direction with the description of vector quantities (even when the direction may not be explicitly sought).

So, for each answer decide whether the horzontal force is directed to the right or the left.
 

FAQ: Propulsive force and force at interface

1. What is propulsive force and how does it work?

Propulsive force is the force that propels an object forward. It is typically generated by a propulsion system, such as a rocket engine or a jet engine, which produces thrust through the expulsion of a high-speed exhaust gas. This thrust creates a reactive force that propels the object in the opposite direction.

2. How is propulsive force related to Newton's third law of motion?

Newton's third law of motion states that for every action, there is an equal and opposite reaction. In the case of propulsive force, the action is the expulsion of exhaust gas, and the reaction is the propulsive force that moves the object in the opposite direction. This law is crucial to understanding how propulsive force works.

3. What factors affect the amount of propulsive force generated?

The amount of propulsive force generated depends on several factors, including the mass of the expelled gas, the speed at which it is expelled, and the efficiency of the propulsion system. Other external factors, such as air resistance and gravity, can also impact the amount of propulsive force.

4. How is force at the interface different from propulsive force?

Force at the interface refers to the force that exists at the boundary between two objects or materials. It is different from propulsive force because it does not necessarily involve the movement of an object. Force at the interface can be either attractive or repulsive, depending on the types of forces involved.

5. Can propulsive force be negative?

No, propulsive force cannot be negative. It is always a positive force that acts in the opposite direction of the expelled gas. If the propulsive force were negative, it would mean that the object is moving in the same direction as the expelled gas, which is not possible according to Newton's third law of motion.

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