3.6 Forces Acting in 2D

3.6 Forces Acting in 2D

Newton's Laws of motion can help you move your stuff!

Resolution of Forces

Draw

Suppose both ends of a wire are attached to the ceiling and make an angle of 40° with it, is holding a weight of 75 newtons.

Draw the free-body diagram for this situation, including all of the relevant forces.

Multiple Choice

Suppose both ends of a wire are attached to the ceiling and make an angle of 40° with it, is holding a weight of 75 newtons. What is the magnitude of the tension in each side of the wire?

• 58.3 newtons

• 69.2 newtons
• 62.8 newtons
• 45.6 newtons

Drag and Drop

A chandelier weighing 120 newtons is suspended by two wires that make an angle of 60° with the ceiling. The horizontal component of tension has a magnitude of ​

Placeholder

, the vertical component has a magnitude of ​

Placeholder

, and the overall magnitude of tension in the wire is ​

Placeholder

.

Drag these tiles and drop them in the correct blank above

34.6 N

60 N

69.3 N

120 N

58 N

87.1 N

30 N

0 N

28.7 N

73.4 N

Draw

A case of mass 5 kilograms is acted upon by the forces   $$F_1$$ ​  and   $$F_2$$ ​  from opposite directions. The force   $$F_1$$ ​ is 35 newtons and acts parallel to the ground, while $$F_2$$ ​ is at an angle θ = –55°. Draw the free-body diagram that represents this situation, including all relevant forces.

Multiple Choice

A case of mass 5 kilograms is acted upon by the forces   $$F_1$$ ​  and   $$F_2$$ ​  from opposite directions. The force   $$F_1$$ ​  is 35 newtons and acts parallel to the ground, while $$F_2$$ ​ is at an angle θ = –55°. Find the magnitude of  $$F_2$$ ​ needed to keep the object in equilibrium.

• 57.8 N
• 35 N

• 61 N

• -57.8 N

You have a refrigerator on a dolly and need to move it.

The entire system weighs 300 N, and you push it for 2.0 seconds with a force of 20 N.

What is the acceleration of the fridge?

How far does it travel after 2 seconds?

Another Type of Problem

Math Response

You push a box in the horizontal direction with a net force of 25.0 Newtons. The weight of the box is 147 Newtons. After it accelerates for 3.0 seconds, how far has it traveled in meters?

Type answer here

Correct Answer: 7.5

Deg^°

Rad

So how do Newton’s laws help us to move stuff?

Consider the ramp at right: the forces have been broken down into components.

The ramp allows us to use less force to lift a box a vertical distance, by offsetting some of the force to the other component.

Moving Stuff

Multiple Choice

Will a box on a dolly feel heavier pushing it up a ramp or across flat ground?

• up a ramp
• it depends on the weight of the box
• it will feel the same
• across flat ground

Draw

A box with a mass of 23 kg is sliding down a ramp tilted at 35° to the horizontal. Ignoring friction, what is the free-body diagram of the box down the ramp?

Multiple Choice

A box with a mass of 23 kg is sliding down a ramp tilted at 35° to the horizontal. Ignoring friction, what is the acceleration of the box down the ramp?

• 3.2 m/s²

• 9.8 m/s²

• 12.8 m/s²

• 6.4 m/s²

• 5.6 m/s²

The Ramp - Force | Energy | Work - PhET Interactive Simulations

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