4.1 Forces

Hooke's Law describes the behaviour of which kind of material under tension?

• plastic
• metals only
• elastic
• non-metals only

If F is force, k is spring constant and x is extension, Hooke's Law tells us that:

• F=k/x
• x=Fk
• k=Fx
• F=kx

Hooke's Law fails when a material reaches its:

• breakdown
• elastic limit
• end of tether
• fracture stress

A graph of extension against force for an elastic material is:

• A downward curve
• An upward curve
• A straight line from any point on the x and y axis
• A straight line from the origin

A spring has a spring constant of 5N/cm.  What is its extension when loaded with 15N?

• 4cm
• 5cm
• 3m
• 3cm

A spring extends 1.5m under load 10N. What is its spring constant?

• 0.15N/m
• 10N/m
• 6.7N/m
• 15N/m

_________ is the unit of Spring Constant

• N

• N/m

• m

The graph shows the relationship between force and extension as a spring is extended. What is another name for point A?

• Point A is the elastic limit

• Point A is the elastic summet

• Point A is the plastic limit

• Point A is the extension limit

What Quantity can you calculate from the graph and give the magnitude of that quantity.  

• distance 4.5 m
• Force 15 N
• spring constant 20 N/m
• spring constant 200 N/m

A force of 470 N is applied to stretch a spring which has a spring constant, k=1100 N/m.  How much does the spring stretch past its free length?

• 0.214 m
• 2.34 m
• 0.427 m
• 5.17 X 10^5 m