Newton's Third Law & Action-Reaction Pairs: Videos & Practice Problems

During a physics experiment, blocks P and Q are placed on a horizontal, frictionless working bench. The masses of the blocks are P = 35 kg and Q = 15 kg respectively. Block P is pushed with a horizontal force of 360 N. Determine the magnitude of the force that block P applies to block Q. 

The starting blocks used by sprinters give them a nearly horizontal acceleration. A 58.0 kg sprinter using a starting block has a nearly horizontal acceleration with a magnitude of 14.5 m/s². 

a) Determine the horizontal force the sprinter has to exert on the starting blocks to generate the acceleration.

b) The sprinter is propelled forward by a force from: i) the sprinter himself ii) the blocks.

A 1200kg stalled truck on a level parking lot is pushed by a small SUV of mass of 650 kg in a direction due north. The SUV is pushing on the truck with a 2200 N horizontal force. Determine the magnitude of the force applied to the SUV by the truck. 

An ill person lies on a stretcher inside an elevator. Determine the absolute value of the force the ill person of mass 65 kg exerts on the stretcher when accelerating vertically upward at 7.5 m/s².

A 120 kg motorcycle in a remote village pulls on a 200 kg cart. The cart is secured to the motorcycle using a hook. During take-off, the rear tyre exerts a 90 N horizontal force against the gravel road. Determine the magnitude of the force exerted by the motorcycle on the cart. Ignore rolling friction.

3 wheeled frictionless toys are placed in contact with each other on a frictionless level bench. Their masses are 1.5 kg, 2.0 kg, and 2.5 kg. The 1.5 kg is on one side, 2.0 kg is on the middle, and 2.5 kg is on the other side. A child applies a 15 N force (in the positive direction) on the 1.5 kg toy. Determine the contact force between the 1.5 kg and 2.0 kg toys.

A 125 kg motorcycle in contact with the road accelerates from rest to 8 m/s in 1.2 s. Determine the magnitude of the friction force in this motion.

A researcher with a mass of 82.0 kg (including a gun) stands on a frictionless wet ground holding a gun. The researcher fires a 25 g bullet horizontally. The bullet acquires a speed of 650 m/s in 1.20 s. Determine the rebound velocity of the researcher, assuming a constant force on the bullet.

A well is fitted with a pulley. A bucket hangs from the pulley using a flexible cable. A person uses the pulley to get themselves into and out of the well. The bucket has a mass of 15.0 kg, and the person's mass is 62.0 kg. How hard should the person pull on the cable to create an upward acceleration of 0.45 m/s²?

A worker of mass 78.0 kg is standing on a digital scale that outputs measurements in kg. Work out the display on the scale when the worker lifts a 42.0 kg box upward, accelerating it at 3.0 m/s².