21 An object is moving on a horizontal frictionless surface. If the net force applied to the object in the direction of motion is doubled, the magnitude of the acceleration of the object is (1) halved (2) doubled (3) unchanged (4) quadrupled

A box of mass 21 kg moves with a constant velocity of (4, 8, –4) m/s. Three forces are exerted on the box by objects in the surroundings. Two of these forces are F 1 = (1,0, 3) Nand É 2 = (-5, –1, 19) N. What is the third force? F3 = ( i ! )N i i

Two crates of fruit  are released from the top of a ramp inclined at 30 degrees from the horizontal and 4.5 meter long. The two crates consist of  an apple crate of mass 20 kg that is placed in front of a watermelon crate of mass 80 kg.  The apple crate has a coefficient of friction of 0.20 while the watermelon crate has a coefficient of friction of 0.15. How long does it take the apple crate to reach the bottom of the incline if it needs to travel a distance of 4.5 meters?

In the figure, a crate of mass m = 83 kg is pushed at a constant speed up a frictionless ramp (0 = 32°) by a horizontal force F. The positive direction of an x axis is up the ramp, and the positive direction of a y axis is perpendicular to the ramp. (a) What is the magnitude of F? (b) What is the magnitude of the normal force on the crate? (a) Number (b) Number i Units Units

Two blocks are connected via a massless rope over a massless, frictionless pulley. Mass M = 10.7 kg, and mass m = 5.12 kg. If they both have a coefficient kinetic friction of 0.372 what will the magnitude of the acceleration of this system be? m 70 40 Units Number