Physics Grade 12 Work & Energy

What is the unit of work?

• kg

• m/s²

• Newton (N)

• Joule (J)

When the direction of the net force and that of displacement is not along the same direction,

• W=F⋅Δd sinθ

• W=F⋅Δd cosθ

• W=F⋅Δd tanθ

• W=F⋅Δd/2

When the angle between net force and the displacement is greater than 90°,

• the work will be 0.

• the work will be a half.

• the work will be negative.

• the work will be the same as a case when the angle is less than 90⋄.

When an object slides over a flat surface, the work done by normal force is

• 0

• mg⋅Δd

• F_a⋅Δd

• F_s⋅Δd

When an object slides down a frictionless ramp which makes an angle of θ degree, the net work is

• 0

• mgΔd cosθ

• mgΔd sinθ

• FnΔd cosθ

An object slides down from a ramp that makes an angle of θ with horizontal. If the surface has a coefficient of friction μ_k, the work done by friction force is

• μ_kmgh cosθ

• -μ_kmgh (cosθ/sinθ)

• μ_kmgh tanθ

• -μ_kmgh tanθ

When the angle between a force and the displacement is 90°, why do you think the work should be 0J?

• It means that the object will be stopped at the end.

• It means that the object must be at rest.

• A perpendicular force does not help the object to speed up or slow down.

• It is just what the formula says.