6. Intro to Forces (Dynamics)

Vertical Forces & Acceleration

Open Question
A 75.0-kg wrecking ball hangs from a uniform, heavy-duty chain of mass 26.0 kg. (b) What is the tension at a point three-fourths of the way up from the bottom of the chain?
Open Question
A 50 kg box hangs from a rope. What is the tension in the rope if: (c) The box has vy = 5.0 m/s and is speeding up at 5.0 m/s^2
Open Question
A 50 kg box hangs from a rope. What is the tension in the rope if: (b) The box moves up at a steady 5.0 m/s?
Open Question
Astronauts in space 'weigh' themselves by oscillating on a spring. Suppose the position of an oscillating 75 kg astronaut is given by x = (0.30 m) sin ((𝝅 rad/s) X t), where t is in s. What force does the spring exert on the astronaut at (a) t = 1.0 s and (b) 1.5 s? Note that the angle of the sine function is in radians.
Open Question
The mass of the sun is 2.0 x 10^30 kg. A 5.0 x 10^14 kg comet is 75 million kilometers from the sun. What is the magnitude of the comet's acceleration toward the sun?
Open Question
A woman has a mass of 55 kg. (a) What is her weight while standing on earth?
Open Question
It takes the elevator in a skyscraper 4.0 s to reach its cruising speed of 10 m/s. A 60 kg passenger gets aboard on the ground floor. What is the passenger's weight (c) After the elevator reaches its cruising speed?
Open Question
It takes the elevator in a skyscraper 4.0 s to reach its cruising speed of 10 m/s. A 60 kg passenger gets aboard on the ground floor. What is the passenger's weight (a) Before the elevator starts moving?
Open Question
Zach, whose mass is 80 kg, is in an elevator descending at 10 m/s. The elevator takes 3.0 s to brake to a stop at the first floor. (a) What is Zach's weight before the elevator starts braking?
Open Question
FIGURE EX6.19 shows the velocity graph of a 75 kg passenger in an elevator. What is the passenger's weight at t=1s? At 5 s? At 9 s?
Open Question
(II) A rocket with a mass of 2.45 x 10⁶ kg is launched by exerting a vertical force of 3.55 x 10⁷ N on the gases it expels. Determine
(a) the acceleration of the rocket, Assume g remains constant, and ignore the mass of gas expelled (not realistic).
Open Question
(II) A woman stands on a bathroom scale in a motionless elevator. When the elevator begins to move, the scale briefly reads only 0.75 of her regular weight. Calculate the acceleration of the elevator, and find the direction of acceleration.
Open Question
(II) What will a spring scale read for the weight of a 58.0‑kg woman in an elevator that moves
(a) upward with constant speed 4.4 m/s,
Open Question
(II) What will a spring scale read for the weight of a 58.0‑kg woman in an elevator that moves
(b) downward with constant speed 4.4 m/s,
Open Question
(II) What will a spring scale read for the weight of a 58.0‑kg woman in an elevator that moves
(d) with a downward acceleration 0.18 g, and