A 70 kg cart is pushed for 50 m with a constant velocity upon a 45º frictionless incline. What is the work done on the cart?

Expert Answers
enotechris eNotes educator| Certified Educator

Work is defined as force through a distance:

1) Work = Force * Distance, or  W=fd

The cart has a mass of 70 kg, subject to the acceleration of gravity, 9.8 m/sec^2.

Force is defined in terms of Newtons (N) as (kg m)/sec^2, so the cart has a force of

70kg * 9.8 m/sec^2 = 686 (kg m)/sec^2 or 686 N

so by formula 1, the Work should be 686N * 50m, however, there's an incline to consider which modifies the force.  Formula 1 is better described as:

2) Work = Force * Distance(cos (theta)), where theta is the angle of the incline.  So the formula should read:

Work = 686N * 50m(cos 45)

=  686N * 50m(.7071)

=  686N * 35.355m

=  24253 Nm

A Newton * meter (Nm) is the same thing as a Joule (J), which is used to express an amount of work, so

=  24253 J


neela | Student

The work done w in moving the mass of m kg to a vertical height h meter is given by: w= mgh, where g is the acceleration due to gravity =9.81m/s^2.

Here height of the 50 m inclination of 45 degree = 50 sin 45.

Therefore, W = 70*g*50cos 45 = 70*9.81*50 sin45 = 24278.51133 J