- A baby carriage with a mass of 50 kg is being pushed along a rough sidewalk with an applied horizontal force of 200 N, and it has a constant velocity of 3.0 m/s.
(A)What other force is acting on the carriage?
(B)What is the magnitude of this force? Answer: 200 N [back]
(C)What value of applied horizontal force would be required to accelerate the carriage from rest to 7.0 m/s in 2.0 s?
Answer: 380 N.
- An empty railway flatcar of mass 15 000 kg is being pulled along a smooth, horizontal track by a tractor travelling on a road parallel
to the track. The rope joining the tractor and the flatcar makes an angle of 25 degrees with the track.
If the acceleration of the flatcar is 0.80 m/s2,
what is the force exerted by the rope on the flatcar? answer: 13000 N at 25 degrees to the track.
- A boy on a toboggan is sliding down a snow-covered hillside. The boy and toboggan have a mass of 50 kg, and the slope is 30 degrees. Find the boy's acceleration if
the kinetic coefficient of friction is 0.15. Answer: 3.6 m/s2
- A plane is flying in a vertical loop of 1500 m radius. At what speed is the plane flying at the top of the loop, if the vertical force
exerted by the plane on the air is zero at this point? 121.2 m/s
- A helium balloon is attached in the exact middle of a
light fishing line which has both ends attached to the level ground. The ends of the line make an angle of 5 degrees to the ground, at both
ends. Find the tension in the fishing line of the upward force of the balloon is 0.05 N. (answer: 0.29 N)
We only did resolving forces questions with three forces, not four, so disregard this question.
- Four children are having a tug-of-war, trying to pull a 100 kg mass. Annie is pulling at 15 N [N], Betty is pulling at 12 N S[30]W,
Cassie is pulling at 20 N S[20]E, and Danny is pulling at 10 N N[10] W.
Find the acceleration of the mass. (answer: 0.044 m/s2 S[11]W)
- 0.50-g insect rests on a compact disc at a distance of 4.0 cm from the centre. The disc's rate of rotation
varies from 3.5 Hz to 8.0 Hz in order to maintain a constant data sampling rate.
(a) What are the insect's minimum and maximum centripetal accelerations during its rotation around the disc?
(b) What is the minimum value of the coefficient of static friction that would prevent the insect from slipping
off the disc at the slowest rotation rate?
ANSWER: (A) min. accel = 19, max. accel = 100 m/s2 [towards center] (B) µ = 2.0 t
- An object of mass 6.0 kg is whirled around in a vertical circle on the end of a 1.0 m long string with a constant
speed of 8.0 m/s. Include a free-body diagram for each of the following questions:
(a) Determine the maximum tension in the string, indicating the position of the object at the time the maximum
tension is achieved.
(ANSWER = 440 N [up] at bottom of circle)
(b) What is the minimum speed the object could be rotated with and maintain a circular path?
(ANSWER = 3.1 m/s2)
- A force of 3.5 N [60°E of N] and a force of 2.8 N [40°W of S] act on the same object. Find the net force acting
on the object using a trigonometric method.
(Answer: 1.3 N E[18]S)
- A spider builds its web in a window frame that is lying on the ground. It is supported by three main strands.
Calculate the force of tension in strand 3 assuming the web is stable. The tensions in the other two strands are
as follows:
strand 1: 21 mN [20°E of N]
strand 2: 16 mN [60°E of S]
strand 3: ______________?W of S]
(Answer: _________
- Two blocks of mass 500.0 g and 200.0 g are suspended vertically as shown in the diagram. The top string is
lifted vertically upward exerting a force of 8.48 N on the 500.0-g block.
A picture of the situation would show a string holding up a 500 g object. The 500 g object has a string coming from it holding up a 200 g object)
(a) At what rate do the blocks rise? (Answer: a = 2.3 m/s2 [up]).
(a) Determine the minimum force required to push a crate along the ramp. Include an appropriate free-body
diagram.
(ANS: The minimum force required to push is 772 N up the ramp.)
(b) If a crate is let go from rest at the top of the ramp and begins to slide, how long will it take to reach the
bottom of the ramp? Include a new free-body diagram.
(ANSWER: It would take 5.9 S to reach the bottom of the ramp)
(c) What minimum value for the coefficient of static friction will prevent the crate from beginning to slide if it is
let go at the top of the ramp?
(ANSWER = The minimum coefficient of static friction required is 0.58.)
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