v(3) = v(6)= A crate of mass m = 10 kg is "lifted" from rest by a rope with a force given by F = 75√t N. Find the speed of the box at t = 3s and at t = 6 s. How much higher is the box, measured from its starting position, at t = 6 s? Use impulse and momentum, I guess y (6)= m S m 8 m m F UBC Engineering

For each of the following situations: a. Choose an initial and final state (states A and B) that will be appropriate (interesting) for analysis. b. If there is not already a physical diagram of the situation and there should be one for proper analysis, include one. c. Construct a system schema of the situation. Do not forget to include the system boundary for the system specified by the problem. Choose your system wisely. d. Construct an energy bar chart and system flow diagram (LOL plots) for each problem. e. You are allowed to add other energy storage modes. You do not have to use the energy storage modes that are printed in each LOL plot. f. Find the unknown value.

Let’s look at a simplified model of a car that’s dropped onto the ground. Model the suspension as a single linear spring and the rest of the vehicle as a single lumped mass. The car is dropped from a height of h1 = 0.9m. What is the maximum mass m for which the suspension does not bottom out? Assume a maximal allowable suspension travel of 10 cm and a spring constant of k = 2.4x10^6 N/m.

graduate who joined the Navy as a pilot is about to take off in an F-15 (WF15 = 81,000 lb) from an aircraft carrier traveling at VA = 40 mph. The jet is launched from the catapult system (a connection just below the deck that assists the aircraft) with the force (Fcp) vs time curve shown that has points of F₁ = 1,000 lb at t₁ = 2 s and F₂ = 3,000 lb at t₂ = 5 s (the plane will reach the edge of the deck at t₂). The F-15 needs to be traveling at 170 mph to take off. Determine how much constant thrust (FTR) the engines must produce during the launch to reach this speed. F2 F₁ FCP t₁ VA t₂ FTR t (s)

A baseball (radius = .0366 m, mass = .145 kg) is dropped from rest at the top of the Empire State Building (height = 1250 ft). Calculate (a) the initial potential energy of the baseball, (b) its final kinetic energy, and (c) the total energy dissipated by the falling baseball by com- puting the line integral of the force of air resistance along the baseball's total distance of fall. Compare this last result to the difference between the baseball's initial potential energy and its final kinetic energy. (Hint: In part (c) make approximations when evaluating the hyperbolic functions obtained in carrying out the line integral.) 2.9

A cord passing over a pulley connects two masses, as shown, where  m1 = 3.80 kg  and  m2 = 7.20 kg.  The system accelerates with a magnitude of 0.94 m/s2. The coefficient of kinetic friction between the masses and the incline is the same for both masses. Assume the pulley is frictionless, and the cord is massless. (Due to the nature of this problem, do not use rounded intermediate values in your calculations—including answers submitted in WebAssign.)   What is the tension (in N) in the cord?

At max load, the elevator E weighs 8000 lb. The counterweight C weighs 3500 lb. Research shows that generally speaking, elevator speeds reach up to 600 ft/min, and are designed to accelerate at about 10 ft/s². If the elevator is at capacity, the motor has an efficiency of 85%, and the mechanical systems (pulleys, cables, etc.) experience various energy losses totaling 30%, find the required power input to the motor if... (a) The elevator is accelerating and moving up at maximum rates. (b) The elevator is moving up at a constant max rate. (c) The elevator is moving down at a constant max rate. E C M

A69 A typical escalator in the London Under- ground rises at an angle of 30° to the horizontal. It lifts people through a vertical height of 15 m in 1.0 minute. Assuming all the passengers stand still whilst on the escalator, 75 people can step on at the bottom and off at the top in each minute. Take the average mass of a passenger to be 75 kg. (a) Find the power needed to lift the passen- gers when the escalator is fully laden. For this calculation assume that any kinetic energy given to the passengers by the escalator is negligible. (b) The frictional force in the escalator system is 1.4 x 10*N when the escalator is fully laden. Calculate the power needed to overcome the friction. Hence find the power input for the motor driving the fully laden escalator, given that the motor is only 70% efficient. (c) When the passengers walk up the moving escalator, is more or less power required by the motor to maintain the escalator at the same speed? Explain your answer. (0 & C, '90]

2. Which of the following momentum equations about B is CORRECT for the system of the golf ball and the golf club?

An ice hockey player of mass m1 = 93.5 kg hits a puck of mass m2 = 0.14 kg, giving the puck a speed of v = 39.5 m/s. a) If both are initially at rest and if the ice is frictionless, how far, in terms of the variables in the problem, does the player recoil in the time it takes the puck to reach the goal, a distance d away?  b)If both are initially at rest and if the ice is frictionless, how far, in centimeters, does the player recoil in the time it takes the puck to reach the goal, 15 m away?