Assignment 11
1. Knight 11.048. [492885]
In the figure, m1 = 3.1 kg. Use work and energy to find the speed of the m2 = 2.3 kg block just before it hits the floor in each of the following cases.
(a) The table is frictionless.
m/s
(b) The coefficient of kinetic friction of the 3.1 kg block is 0.15.
m/s
2. Knight 11.054. [380267]
The spring shown in Figure P11.54 is compressed 35 cm and used to launch a 100 kg physics student. The track is frictionless until it starts up the incline. The student's coefficient of kinetic friction on the 30° incline is 0.13.
Figure P11.54
(a) What is the student's speed just after losing contact with the spring?
m/s
(b) How far up the incline does the student go?
m (measured along the incline)
3. Knight 11.034. [455131]
A particle moves from A to D in Figure P11.34 while experiencing force = (7 + 9 ) N. How much work does the force do if the particle follows the following paths?
Figure P11.34
(b) ACD / J
(c) AD / J
Is this a conservative force?
yes
no
4. Knight 11.028. [380226]
(a) How much work does an elevator motor do to lift a 980 kg elevator a height of 92 m?
J
(b) How much power must the motor supply to do this in 48 s at constant speed?
W
5. Knight 11.015. [455118]
A 400 g particle moving along the x-axis experiences the force shown in Figure Ex11.15. The particle goes from vx = 1.5 m/s at x = 0 m to vx = 7.5 m/s at x = 2 m. What is Fmax?
N
Figure Ex11.15
6. Knight 11.010. [492883]
The two ropes shown in the bird's-eye view of Figure Ex11.10 are used to drag a crate 2.9 m across the floor, with fk = 455 N, T1 = 296.01 N and = 27°. How much work is done by each of the three forces?
k / J1 / J
2 / J
Figure Ex11.10
7. Knight 11.009. [455119]
The two ropes seen in Figure Ex11.9 are used to lower a 230 kg piano 6.0 m from a second-story window to the ground. How much work is done by each of the three forces? (T1 = 1820 J andT2 = 1210 J)
Figure Ex11.9
T1 / J
T2 / J
8. Knight 11.005. [380263]
How much work is done by the force = (6.0 - 2.0 ) N on a particle that moves through the following displacements?
(a) = 2.0 m
J
(b) = 2.0 m
J
9. Knight 11.001. [492878]
Evaluate the dot product of the three pairs of vectors in Figure Ex11.1, with A = 9, D = 6, and F = 6.
Figure Ex11.1
(a)
(b)
(c)