PHYS 2211 Module 5 Self Assessment Practice Problems

Module 5 Self Assessment Practice Problems

5.1
While sliding a couch across a floor, Andrea and Jennifer exert forces and on the couch. Andrea’s force is due north with a magnitude of 130.0 N and Jennifer’s force is 32° east of north with a magnitude of 180.0 N.
(a) Find the net force in component form.
(b) Find the magnitude and direction of the net force.
(c) If Andrea and Jennifer’s housemates, David and Stephanie, disagree with the move and want to prevent its relocation, with what combined force should they push so that the couch does not move?
Answer: (a) N (b) 299 N at 71° north of east (c) N
5.2

The net external force on the 24-kg mower is given as 51 N.
(a) If the force of friction opposing the motion is 24 N, what force (in newtons) is the person exerting on the mower?
(b) Suppose the mower is moving at 1.5 m/s when the force is removed. How far will the mower go before stopping?
Answer: (a) 75 N (b) 1.1 m
5.3
A powerful motorcycle can produce an acceleration of 3.50 m/s2 while traveling at 90.0 km/h. At that speed, the forces resisting motion, including friction and air resistance, total 400.0 N. (Air resistance is analogous to air friction. It always opposes the motion of an object.) What is the magnitude of the force that motorcycle exerts backward on the ground to produce its acceleration if the mass of the motorcycle with rider is 245 kg?
Answer: 1.26 x 103 N
5.4

Find the acceleration of the body of mass 5.0 kg shown.
Answer:
5.5
A baseball catcher is performing a stunt for a television commercial. He will catch a baseball (mass 145 g) dropped from a height of 60.0 m above his glove. His glove stops the ball in 0.0100 s. What is the force exerted by his glove on the ball?
Answer: 499 N
5.6
A body of mass 2.00 kg is pushed straight upward by a 25.0 N vertical force. What is its acceleration?
Answer: 2.7 m/s2
5.7
A truck collides with a car, and during the collision, the net force on each vehicle is essentially the force exerted by the other. Suppose the mass of the car is 550 kg, the mass of the truck is 2200 kg, and the magnitude of the truck’s acceleration is 10 m/s2. Find the magnitude of the car’s acceleration.
Answer: 40 m/s2
5.8
A brave but inadequate rugby player is being pushed backward by an opposing player who is exerting a force of 800.0 N on him. The mass of the losing player plus equipment is 90.0 kg, and he is accelerating backward at 1.20 m/s2.
(a) What is the force of friction between the losing player’s feet and the grass?
(b) What force does the winning player exert on the ground to move forward if his mass plus equipment is 110.0 kg?
Answer: (a) 692 N (b) 932 N
5.9
A large rocket has a mass of 2.00 x 106 kg at takeoff, and its engines produce a thrust of 3.50 x 107 N.
(a) Find its initial acceleration if it takes off vertically.
(b) How long does it take to reach a velocity of 120 km/h straight up, assuming constant mass and thrust?
Answer: (a) 7.70 m/s2 (b) 4.33 s
5.10
An elevator filled with passengers has a mass of 1.70 x 103 kg.
(a) The elevator accelerates upward from rest at a rate of 1.20 m/s2 for 1.50 s. Calculate the tension in the cable supporting the elevator.
(b) The elevator continues upward at constant velocity for 8.50 s. What is the tension in the cable during this time?
(c) The elevator decelerates at a rate of 0.600 m/s2 for 3.00 s. What is the tension in the cable during deceleration?
Answer: (a) 1.87 x 104 N (b) 1.67 x 104 N (c) 1.56 x 104 N