Acceleration, distance, and friction

AI Thread Summary
The discussion revolves around a physics problem involving a skater with a mass of 78 kg who exerts a constant force of 137 N for 3.3 seconds while skating on ice with a friction coefficient of 0.007. The initial calculation of acceleration was found to be 1.74 m/s², but the impact of friction was not initially considered. Participants clarified that the friction force must be calculated using the normal force, which is equal to the weight of the skater, not the pushing force. To solve for final velocity and distance, the kinematic equations for constant acceleration should be applied, starting with the correct friction force calculation. Understanding the relationship between friction, normal force, and acceleration is essential for completing the problem.
npena29
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heres a problem I am stuck on..can someone please help me?

a skater has a mass of 78 kg is pushes with a constant force of 137N for a time of 3.3 sec on the ice. the coefficient of friction of the blades against the ice is 0.007.

1. find the skaters acceleration, taking friction into account.
2. how fast is the skater going at the end of the push?
3. how much distance has the skater covered during the push?

what i first did was find acceleration
a=f/m i got 1.74 m/s2
now what I am stuck on is part 2 and 3...is the Final Velocity and Intial Velocity zero?

someone please help me start off this problem :)
 
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When you calculated the acceleration, did you account for the friction force acting opposite the pushing force? It's a rather small number, but you should include it. Once you get the acceleration, yes, the initial velocity is 0, but to get the final velocity and distance traveled after 3.3 seconds, you need to use the kinematic motion equations for constant acceleration.
 
how will i calculate the friction force and how is it applied?
 
npena29 said:
how will i calculate the friction force and how is it applied?
I would think you would have studied friction at this point. Sliding frictional forces are the product of the the kinetic friction coefficent times the Normal force (the normal force is the force perpendicular to the surface), and are always in the direction that is opposite to the direction of the relative motion between the 2 surfaces (the friction force is parallel to the surface).
 
ok..i got that formula now...so will it be friction=(0.007)(137N)
and i get .959
 
npena29 said:
ok..i got that formula now...so will it be friction=(0.007)(137N)
and i get .959
No, the normal force is not 137 N. What is the normal force acting on the skater?
 
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