Download AP_B_Forces_HW_2010... - Jaclyn Kuspiel Murray

AP B Forces HW 2010
1.
In a grocery store, you push a 17.5 kg shopping cart with a force of 11.0 N. If the cart starts at
rest, how far does it move in 3.00 s?
m
2.
A 0.66 kg ball initially at rest is given a speed of 10.5 m/s during a time interval of 3.4 ms. What
average force acted on the ball during this time?
kN
3.
Driving home from school one day you spot a ball rolling out into the street (Figure 5-18). You
brake for 1.25 s, slowing your 1120 kg car from 16.0 m/s to 9.50 m/s.
Figure 5-18
(a) What was the average force exerted on your car during braking?
Magnitude
kN
Direction
backward
forward
(b) How far did you travel while braking?
m
4.
A shopper pushes a 8.9 kg shopping cart up a 13° incline, as shown in Figure 5-24. Find the
magnitude of the horizontal force, F, needed to give the cart an acceleration of 1.43 m/s2.
N
Figure 5-24
5.
Two crewmen pull a boat through a lock, as shown in Figure 5-25. One crewman pulls with a
force of F1 = 145 N at an angle of θ = 31° relative to the forward direction of the raft. The
second crewman, on the opposite side of the lock, pulls at an angle of 45°. With what force F2
should the second crewman pull so that the net force of the two crewmen is in the forward
direction?
N
Figure 5-25
6.
A 75 kg skier speeds down a trail, as shown in Figure 5-24. The surface is smooth and inclined at
an angle of θ = 18° with the horizontal.
Figure 5-24
(a) Draw a free-body diagram for the skier. (Do this on paper. Your instructor may ask you to
turn in this diagram.)
Key: paper submission
(b) Determine the magnitude of the normal force acting on the skier.
N
7.
A baseball player slides into third base with an initial speed of 7.95 m/s. If the coefficient of
kinetic friction between the player and the ground is 0.44, how far does the player slide before
coming to rest?
m
8.
When you push a 1.60 kg book resting on a tabletop it takes 2.20 N to start the book sliding.
Once it is sliding, however, it takes only 1.50 N to keep the book moving with constant speed.
What are the coefficients of static and kinetic friction between the book and the tabletop?
static
kinetic
9.
You want to nail a 1.2 kg board onto the wall of a barn. To position the board before nailing, you
push it against the wall with a horizontal force F to keep it from sliding to the ground.
Figure 6-30
(a) If the coefficient of static friction between the board and the wall is 0.93, what is the least
force you can apply and still hold the board in place?
N
(b) What happens to the force of static friction if you push against the wall with a force greater
than that found in part (a)?
stays the same
decreases
increases
10.
A bag of cement of weight 475 N hangs from three wires as suggested in the figure below. Two
of the wires make angles θ1 = 55.0° and θ2 = 28.0° with the horizontal. Assuming the system is
in equilibrium, find the tensions in the wires.
T1 =
T2 =
T3 =
11.
N
N
N
A block of mass m = 2.00 kg is released from rest at h = 0.500 m from the surface of a table, at
the top of a θ = 20.0° incline as shown below. The frictionless incline is fixed on a table of
height H = 2.00 m.
(a) Determine the acceleration of the block as it slides down the incline.
m/s2
(b) What is the velocity of the block as it leaves the incline?
m/s
(c) How far from the table will the block hit the floor?
m
(d) How much time has elapsed between when the block is released and when it hits the floor?
s
(e) Does the mass of the block affect any of the above calculations?
Yes
No
12.
To give a 15 kg child a ride, two teenagers pull on a 3.4 kg sled with ropes, as indicated in Figure
5-26. Both teenagers pull with a force of F = 65 N at an angle of 35° relative to the forward
direction, which is the direction of motion. In addition, the snow exerts a retarding force on the
sled that points opposite to the direction of motion, and has a magnitude of 57 N. Find the
acceleration of the sled and child.
m/s2
13.
A 63 kg skier speeds down a trail, as shown in Figure 5-27. The surface is smooth and inclined at
an angle of θ = 21° with the horizontal.
Figure 5-27
(a) Find the direction and magnitude of the net force acting on the skier.
Magnitude
N Direction
perpendicular from the slope (away from ground)
ground)
towards the center of the earth
center of the earth
perpendicular from the slope (into the
uphill, parallel to slope
away from the
downhill, parallel to slope
(b) Does the net force exerted on the skier increase, decrease, or stay the same as the slope
becomes steeper?
stay the same
increase
decrease