Uniform Circular Motion

pg. 64 #30- A 1200kg car is travelling at 25m/s on a horizontal surface in a circular path of radius 85m. What is the net force acting on this car?

What is step 1?

1. Find the equation needed:

Fc=mv^2/r

pg. 64 #30- A 1200kg car is travelling at 25m/s on a horizontal surface in a circular path of radius 85m. What is the net force acting on this car?

What is step 2?

The second step is to plug in the numbers.

m=1200

v=25

r=85

Fc=1200(25)^2/85

Answer = 8.8x10^3N (B)

pg. 64 #31- A 61kg skateboarder is moving down a ramp with a 7.0m radius of curvature. At the bottom of this ramp he reaches a speed of 7.8m/s. What upward force acts on the skateboarder at the bottom of the ramp?

What is the first step?

Fc=mv^2/r

Fn-Fg=mv^2/r

pg. 64 #31- A 61kg skateboarder is moving down a ramp with a 7.0m radius of curvature. At the bottom of this ramp he reaches a speed of 7.8m/s. What upward force acts on the skateboarder at the bottom of the ramp?

What is the second step?

Rearrange the equation.

Fn=mv^2/r+Fg

pg. 64 #31- A 61kg skateboarder is moving down a ramp with a 7.0m radius of curvature. At the bottom of this ramp he reaches a speed of 7.8m/s. What upward force acts on the skateboarder at the bottom of the ramp?

What is the third step?

Plug into the equation:

m=61

v=7.8

r=7.0

Fg= 61(9.81)

Fn=61(7.8)^2/7.0 + 61(9.81)

Answer= 1.1x10^3N (D)