Force Calculation: Help with Question 8

  • Thread starter Thread starter jjg242
  • Start date Start date
AI Thread Summary
To calculate the force exerted on the board by the karate master, the relevant equations are momentum and impulse, represented as mv = Ft. The change in velocity is determined by subtracting the final velocity (1 m/s) from the initial velocity (10 m/s), resulting in a change of 9 m/s. Using the mass of the hand and arm (1 kg) and the contact time (0.002 s), the force can be calculated as F = (mass * change in velocity) / time, leading to a force of 4500 N. The discussion confirms this calculation is correct, and additional resources for understanding impulse and momentum are provided.
jjg242
Messages
12
Reaction score
0
8. A karate master strikes a board with an initial velocity of 10 m/s, decreasing to 1 m/s as his hand passes through the board. If the time of contact with the board is 0.002 s, and the mass of the coordinated hand and arm is 1 kg, what is the force exerted on the board.

a. 1000 N
b. 1800 N
c. 2700 N
d. 4500 N

- well, I lost my book because my backpack got stolen and I have an older physics book i got from a friend and the pages don't match up with my study guide. I can't find the right equation for this. I need an equation that uses change in velocity, contact time, and mass of the object to get F in Newtons. If anyone can show me how I do this or at least point me in the right direction I would appreciate it.
 
Physics news on Phys.org
Momentum=Impulse

mv=Ft
 
laminar said:
Momentum=Impulse

mv=Ft

so...

m = mass
v= change in velocity?
F= force in N
t= time

is v the initial, final, or change in velocity?

if it is change in velocity, then i get:

9*1/0.002 = 4500 N

Is this right?
 
Last edited:
bump. any feedback appreciated.
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'Calculation of Tensile Forces in Piston-Type Water-Lifting Devices at Elevated Locations'
Figure 1 Overall Structure Diagram Figure 2: Top view of the piston when it is cylindrical A circular opening is created at a height of 5 meters above the water surface. Inside this opening is a sleeve-type piston with a cross-sectional area of 1 square meter. The piston is pulled to the right at a constant speed. The pulling force is(Figure 2): F = ρshg = 1000 × 1 × 5 × 10 = 50,000 N. Figure 3: Modifying the structure to incorporate a fixed internal piston When I modify the piston...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top