Question
#2 Please answer the question neatly with steps and show all units, for good rating!
is 20Nm. How far will the spring be compressed? What is the change in the gravitational energy of the mass? (c) What is the change in elastic potential energy of the spring? (Ignore any loss of energy in joining of the mass with the end of the spring and ignore the mass of the spring. Assume bottom end of the spring is rigidly held in place.) 2. An 800kg roller coaster initially moving at 8.5m/s comes dawn its tracks a distance of 300m measured along its tracks, as shown. (a)if the friction force is an average of 800N for the full run of the track, what will its speed be at the bottom? Assume the vertical drop of the track is 35m and the actual run of the track is 300m, as shown below. b) How much work is done by the farce of friction?; by the normal force?; and by the force of gravity? (Hint: Don't forget that gravity is a conservative force and that friction is not aconservative force.) Act LA0.20kg tennis ball moving at 20.0m/s is struck by a racket causing the ball to rebound in the opposite direction at a speed of 30.0m/s. What is the change in momentum of the ball? (b) What is the impulse of the ball? fe What is the average force acting on the ball during the
Explanation / Answer
here,
mass , m = 800 kg
u = 8.5 m/s
distance , s = 300 m
a)
friction force , ff = 800 N
x = 300 m , h = 35 m
let the speed of bottom be v
kinetic energy gained = potential energy lost + work done by friction
0.5 * m * (v^2 - u^2) = m * g * h - ff * x
0.5 * 800 * ( v^2 - 8.5^2) = 800 * 9.81 * 35 - 800 * 300
v = 12.1 m/s
b)
the work done by the frictional force , Wff = - ff * x
Wff = - 800 * 300 J
Wff = - 2.4 * 10^5 J
the work done by normal force , Wn = - m * g * h
Wn = - 800 * 9.81 * 35 J
Wn = 2.75 * 10^5 J
the work done by gravity , Wg = m * g * h
Wg = 800 * 9.81 * 35 J
Wg = 2.75 * 10^5 J
