Final answer:
To lift a crate at constant speed, the force applied must equal the weight of the crate, calculated as mass times gravity. When accounting for friction, this force must also overcome the frictional force. Work done is computed by multiplying the lifting force by the height of the lift.
Step-by-step explanation:
To lift a crate with a constant speed, one must apply a force that is equal to the gravitational force acting on the crate, otherwise known as the weight of the crate. The weight is calculated by multiplying the mass of the crate by the acceleration due to gravity (9.81 m/s2). For example, if you have a 40-kg crate, the magnitude of the force required to lift it with constant speed would be 40 kg × 9.81 m/s2 = 392.4 N (Newtons).
In a scenario where there is friction, such as sliding a crate across a rough surface, the force required to maintain constant speed must also overcome the force of friction. This would require calculating the normal force, then applying the coefficient of friction to find the frictional force, and finally adding this to the gravitational force to find the total force needed.
Work is the product of force and displacement. To compute the work done in lifting the crate, you multiply the force required to lift the crate by the height it is lifted.