BackSuperman must stop a 120-km/h train in 150 m to keep it from hitting a stalled car on the tracks. If the train's mass is 3.6 x 10⁵ kg, how much force must he exert? Compare to the weight of the train (give as %). How much force does the train exert on Superman?
An 18-kg child is riding in a child-restraint chair, securely fastened to the seat of a car (Fig. 4–69). Assume the car has speed 45 km/h when it hits a tree and is brought to rest in 0.20 s. Assuming constant deceleration during the collision, estimate the net horizontal force F that the straps of the restraint chair exert on the child to hold her in the chair. <IMAGE>
When jumping straight up from a crouched position, an average person can reach a maximum height of about cm. During the jump, the person's body from the knees up typically rises a distance of around cm. To keep the calculations simple and yet get a reasonable result, assume that the entire body rises this much during the jump. Draw a free-body diagram of the person during the jump.
What is the acceleration, as a multiple of g, if this force is applied to a 110 kg bicyclist? This is the combined mass of the cyclist and the bike.
If a car stops suddenly, you feel 'thrown forward.' We'd like to understand what happens to the passengers as a car stops. Imagine yourself sitting on a very slippery bench inside a car. This bench has no friction, no seat back, and there's nothing for you to hold onto. Describe what happens to you as the car slows down.
On September 8, 2004, the Genesis spacecraft crashed in the Utah desert because its parachute did not open. The -kg capsule hit the ground at km/h and penetrated the soil to a depth of cm. What was its acceleration (in m/s2 and in g's), assumed to be constant, during the crash?
An astronaut is inside a kg rocket that is blasting off vertically from the launch pad. You want this rocket to reach the speed of sound ( m/s) as quickly as possible, but astronauts are in danger of blacking out at an acceleration greater than . What force, in terms of the astronaut's weight , does the rocket exert on her? Start with a free-body diagram of the astronaut.
An astronaut is inside a kg rocket that is blasting off vertically from the launch pad. You want this rocket to reach the speed of sound ( m/s) as quickly as possible, but astronauts are in danger of blacking out at an acceleration greater than . What is the maximum initial thrust this rocket's engines can have but just barely avoid blackout? Start with a free-body diagram of the rocket.
A light rope is attached to a block with mass kg that rests on a frictionless, horizontal surface. The horizontal rope passes over a frictionless, massless pulley, and a block with mass is suspended from the other end. When the blocks are released, the tension in the rope is N. Draw two free-body diagrams: one for each block.
On September 8, 2004, the Genesis spacecraft crashed in the Utah desert because its parachute did not open. The -kg capsule hit the ground at km/h and penetrated the soil to a depth of cm. What force did the ground exert on the capsule during the crash? Express the force in newtons and as a multiple of the capsule's weight.
Problems 35, 36, 37, 38, 39, and 40 show a free-body diagram. For each: Identify the direction of the acceleration vector a and show it as a vector next to your diagram. Or, if appropriate, write a = 0.
FIGURE EX5.14 shows an object's acceleration-versus-force graph. What is the object's mass?
A constant force is applied to an object, causing the object to accelerate at 10 m/s². What will the acceleration be if The force is halved and the object's mass is doubled?
A constant force is applied to an object, causing the object to accelerate at 10 m/s². What will the acceleration be if the force is halved?
A single force with x-component Fₓ acts on a 2.0 kg object as it moves along the x-axis. A graph of Fₓ versus t is shown in FIGURE P5.32. Draw an acceleration graph aₓ versus t) for this object.