You and your brother argue often about how to safely secure a toddler in a moving car. You insist that special toddler seats are critical in improving the chances of a toddler surviving a crash. Your brother claims that, as long as his wife is buckled in next to him with a seat belt while he drives, she can hold onto their toddler on her lap in a crash. You decide to perform a calculation to try to convince your brother. Consider a hypothetical collision in which the 12-kg toddler and his parents are riding in a car traveling at 60 mi/h relative to the ground. The car strikes a wall, tree, or another car, and is brought to rest in 0.10 s. You wish to demonstrate to your brother the magnitude of the force necessary for his wife to hold onto their child during the collision.
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Chapter 9 Solutions
Physics for Scientists and Engineers
- A meter stick has a mass of 0.5 kg and a center of mass at the 50 cm mark. Using two fingers, one at the 10 cm mark and the other at the 40 cm mark, you hold the meter stick in a stationary horizontal position. Find the forces that your fingers put on the meter stick.arrow_forwardAnswer 1 and 2 please 1. Suppose you are in an enclosed boxcar, initially at rest on a track with no friction. You throw heavy darts at the front wall of the car which stick right into it. You MAY IGNORE DRAG FRICTION of the darts while they are in the air. Describe the motion of the cart. Select one: i) The cart does not move. ii) The cart moves backwards while the darts are in the air and stops completely when the dart impacts the front wall. iii) The cart moves backwards while the dart is in the air and slows down a bit but is still going backward slowly after the dart’s impact. iv) The cart moves forward slowly. v) The cart moves backwards while the dart is in the air and moves forwards slowly after impact. 2. Suppose you are in an enclosed boxcar, initially at rest on a track with no friction. You throw heavy darts at the front wall of the car which stick right into it. You MAY NOT IGNORE DRAG FRICTION of the darts while they are in the air. Describe the motion of the cart.…arrow_forwardMy sister Crystal of mass M1= 50 kg is on an ice-covered sidewalk with her dog Buster, who has mass M2= 38 kg. They are initially a distanced= 5.0 m apart.By pulling on the massless leash, my sister exerts a constant force F= 30.0 N on Buster; Buster slides towards her. How fast is Buster moving when he and my sister meet? (The leash is not rigid, so the distance can change between them. They also end up at the same point, which means even if you can’t solve for their position,you can set them equal to one another.)arrow_forward
- Usually, we do not walk or even stand on a lightweight boat or raft because of the danger of falling into the water. If you have ever stepped off a small boat onto a dock, however, you have probably noticed that the boat moves away from the dock as you step toward the dock or out of the boat. A heavy dog running on a long lightweight raft presents a similar situation. At first, the raft and the dog are at rest with respect to the water (see figure A below) so that vi = 0. The dog then runs on top of the raft at vd = vd with respect to the water (see figure B below). The dog has half the mass of the raft. Find an expression for the velocity of the raft after the dog began running. (Use the following as necessary: vd.)arrow_forwardUsually, we do not walk or even stand on a lightweight boat or raft because of the danger of falling into the water. If you have ever stepped off a small boat onto a dock, however, you have probably noticed that the boat moves away from the dock as you step toward the dock or out of the boat. A heavy dog running on a long lightweight raft presents a similar situation. At first, the raft and the dog are at rest with respect to the water (see figure A below) so that ✓; = 0. The dog then runs on top of the raft at ✓d = v₁₁ with respect to the water (see figure B below). The dog has one fourth the mass of the raft. Find an expression for the velocity of the raft after the dog began running. (Use the following as necessary: Vd.) V A. √₁ = ? B. V₁ = 0arrow_forwardAn unfortunate astronaut loses his grip during a spacewalk and finds himself floating away from the space station, carrying only a rope and a bag of tools. First he tries to throw a rope to his fellow astronaut, but the rope is too short. In a last ditch effort, the astronaut throws his bag of tools in the direction of his motion, away from the space station. The astronaut has a mass of ?a=102 kg and the bag of tools has a mass of ?b=10.0 kg. If the astronaut is moving away from the space station at ?i=1.50 m/s initially, what is the minimum final speed ?b,f of the bag of tools with respect to the space station that will keep the astronaut from drifting away forever? ?b,f = ? m/sarrow_forward
- You have been called to testify as an expert witness in a trial involving a head-on collision. Car A weighs 15151515 lb and was traveling eastward. Car B weighs 11251125 lb and was traveling westward at 41.041.0 mph. The cars locked bumpers and slid eastward with their wheels locked for 18.518.5 ft before stopping. You have measured the coefficient of kinetic friction between the tires and the pavement to be 0.7500.750. How fast (in miles per hour) was car A traveling just before the collision? (This problem uses English units because they would be used in a U.S. legal proceeding.)arrow_forwardJames (mass 90.0 kg) and Ramon (mass 60.0 kg) are 20.0 m apart on a frozen pond. Midway between them is a mug of their favorite beverage. They pull on the ends of a light rope stretched between them. When James has moved 6.0 m toward the mug, how far and in what direction has Ramon moved?arrow_forwardA 20.0 kg wood ball hangs from a 1.10 m -long wire. The maximum tension the wire can withstand without breaking is 300 N. A 0.900 kg projectile traveling horizontally hits and embeds itself in the wood ball. A) What is the largest speed this projectile can have without causing the cable to break?arrow_forward
- intro to physics, thank you! You set up a 20 cm tall ramp on a 75 cm tall table. The ramp is inclined at 30° to the horizontal.You place a 500 g block at the end of the ramp, and release a 750 g block from rest at the topof the ramp. The ramp exerts 1.6 N of friction on the block. The two blocks are equippedwith velcro so they stick together after colliding. The ramp is designed so the objects travelhorizontally off the table immediately after colliding.(a) How fast are the two blocks traveling just after the collision?(b) How far from the table do they land?arrow_forwardPlease solve and answer the question correctly. Thank you!!arrow_forwardAn M1 Garand rifle has a 0.610 m long barrel. When fired, a bullet with a mass of 11.0 g accelerates from rest and exits the barrel at a speed of 850 m/s. What is the net force on the bullet (in N) while it is in the barrel?arrow_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning