SPH4U 2.3 Applying Newton’s Laws of Motion
1. Objects in equilibrium
Equilibrium:
A sled has a mass of 14 kg and is on a hill that is inclined 25° to the
horizontal, as shown to the right. The hill is very icy (negligible
friction), and the sled is held at rest by a rope attached to a post. The
rope is parallel to the hill as shown.
Draw a FBD.
Calculate the magnitude of the tension in the rope.
Calculate the magnitude of the normal force acting on the sled.
Your car is stuck in the snow. You tie a rope to it, then you
and your friend pull the rope with a force of 103 N, but it
doesn’t move. Then you try tying the free end of the rope
to a tree, and pulling on the rope in the middle, as shown
in the diagram. The car just starts to move! What tension
force does the car experience, and why does this work?
2. Accelerating objects
Newton’s 2nd Law:
Positive x-axis:
A sled is at the top of a hill, which makes an angle of 18° with the
horizontal. The height of the hill is 25 m. Calculate the speed of the
sled as it reaches the bottom of the hill. Assume that no friction acts
on the sled.
A crate with a mass of 32.5 kg sits on a frictionless surface and is connected to
a second crate by a string that passes over a pulley. The second crate has a
mass of 40.0 kg. The pulley is frictionless and has no mass. The string also has
no mass. Determine the acceleration of the system of crates and the
magnitude of the tension in the string.
Homework:
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