Mechanics quesiton. Skateboarder on ramp.

  • Thread starter Thread starter milan.007
  • Start date Start date
  • Tags Tags
    Mechanics Ramp
Click For Summary
SUMMARY

The discussion revolves around the physics problem of a skateboarder accelerating down a ramp. The skateboarder, with a mass of 70 kg, accelerates down a 25m ramp at a 20-degree angle, achieving a velocity of 12.2 m/s at the bottom. Key calculations include determining the average acceleration using the formula \( a = \frac{v^2}{2s} \), finding the parallel component of weight, and analyzing the centripetal force when entering a circular ramp of radius 10m. The participants emphasize the importance of free body diagrams for accurate force analysis.

PREREQUISITES
  • Understanding of kinematics, specifically acceleration calculations.
  • Knowledge of free body diagrams and force decomposition.
  • Familiarity with centripetal force equations, specifically \( F = \frac{mv^2}{r} \).
  • Basic principles of energy conservation, particularly \( \frac{1}{2}mv^2 = mgh \).
NEXT STEPS
  • Review the derivation and application of kinematic equations in physics.
  • Study the principles of free body diagrams and their role in force analysis.
  • Learn about frictional forces and their impact on motion in inclined planes.
  • Explore centripetal motion and the calculations involved in circular dynamics.
USEFUL FOR

Students studying physics, particularly those focusing on mechanics, as well as educators looking for practical examples of kinematic and dynamic principles in action.

milan.007
Messages
9
Reaction score
0

Homework Statement


A skateboarder with total mass of 70kg starts from rest at the top of a ramp and accelerates down it. The ramp is 25m long and is at an angle of 20 degrees to the horizontal. The skateboarder has a velocity of 12.2m/s at the bottom of the ramp.


Calculate
i) the average acceleration of the skate boarder on the ramp.
ii) the component of the skateboarders weight that is parallel to the ramp.
iii) the force of riction acting on the skateborader on the ramp.

The skateboarder then maintains a speed of 10.5m/s until he enters a circular ramp of radius 10m.
What is the initail centripetal force on him?
What is his maximum height achieved?


Homework Equations





The Attempt at a Solution


I used v^2 = u^2 + 2as to get the acceleration
I i found his weight 686N and used sin21=686/x, to find the parallel component.
Then for friction i substituted the parelel component from his weight (i think this is wrong).

For the second part, i used F=mv^2/r to find the centripetal force.
Thn i used 1/2mv^2 = mgh to ind the height.

Can someone do it and tell me if i used the correct formulas and please write the answers i want to compare them.
 
Physics news on Phys.org
You're on the right track, you got the first question right.
aaverage = vf²/2s (Since vi=0)

I lost you at how you found the parallel component, though, try making a free body diagram of the skateboarder, and breaking mg down into its parallel and orthogonal components, relative to the ramp, using the 20° slope.

For the third question, I would approach with caution. Look at your free body diagram and your answers for questions i and ii.
Hint:
This will come in handy here: ΣF = m*a

As for the second question, could you please define it a bit more clearly? Does the friction continue to act on him? Because if so, then this question requires an integral of the force of friction to solve (If I remember the solution correctly), and I doubt that's what the teacher's aiming for, judging by the other questions.

Assuming there's no friction though, then yes, your solution looks correct. :)
 
k thanks
 

Similar threads

Loop problem with skier on ramp going into a loop-the-loop
  • · Replies 13 ·
Replies
13
Views
2K
Skateboarding Down a Ramp: Finding Speed at Bottom
  • · Replies 1 ·
Replies
1
Views
4K
Coefficient of friction of a Skateboard on a ramp
  • · Replies 11 ·
Replies
11
Views
10K
A 1130-kg car is held in place by a light cable on a frictionless ramp
  • · Replies 5 ·
Replies
5
Views
5K
Calculating Spring Stretch on a Ramp with Varying Acceleration and Friction
  • · Replies 3 ·
Replies
3
Views
3K
Find the tension in the cable and the force the ramp exerts on the tires
  • · Replies 8 ·
Replies
8
Views
5K
A wood block is launched up a ramp
  • · Replies 21 ·
Replies
21
Views
5K
Calculating Acceleration of Skateboarder on 11.9m Ramp
  • · Replies 1 ·
Replies
1
Views
3K
Motion on Inclined ramp with Friction Problem
  • · Replies 21 ·
Replies
21
Views
4K
How Does a Speck of Dust Affect the Motion of a Box on an Inclined Ramp?
  • · Replies 33 ·
2
Replies
33
Views
4K