# Physics: Magnitude of force & acceleration

For the following questions, the answers are given but I need the workings to arrive at the answer.

1. A force acts on a 1.5 kg, mass, giving it an acceleration of 3.0 m/s^2. (a) If the same force acts on a 2.5 kg mass, what acceleration would be produced? (b) What is the magnitude of force?

Answer: (a) 1.8m/s^2 (b) 4.5 N

2. An object (mass 10 kg) slides upward on a slippery vertical wall. A force F of 60 N acts at an angle of 60*. (a) Determine the normal force exerted on the object by the wall. (b) Determine the objects acceleration.

Answer: (a) 30N (b) -4.60 m/s^2

3. During a daring rescue, a helicopter rescue squad initially accelerates a little girl (mass 25 kg) vertically off the roof of a burning building. They do this by dropping a rope down to her, which she holds on to as they pull her up. Neglect the mass of the rope. (a) What force causes the girl to accelerate vertically upward (1) her weight; (2) the pull of the helicopter on the rope (4) the pull of the rope on the girl

(b) Determine the pull of the rope (tension) if she initially accelerates upwards at 0.750 m/s^2.

Answer: (a)The correct answer is 4th option, the pull of the rope on girl (b) 264N

4. The weight of the 500 kg object is 4900 N. (a) When the object is on a moving elevator, its measure weight could be (1) zero. (2) between zero to 4900N (3) more than 4900N, (4) all of the preceeding. WHY? (b) Describe the motion if the objects measured weight is only 4000N in a moving elevator.

Answer: (a) N is the measure weight and can take any value, depending on acceleration. Thus 4th option. (b) The elevator must be accelerating downward at 1.8 m/s^2.

5. A girl pushes a 25 kg lawn mower. If F=30N and @ = 37*. (a)What is the acceleration of the mower? (b) What is the normal force exerted on the mower by the lawn? Ignore friction.

Answer: (a) 4.96 m/s^2 (b) 2.6 x 10^2 N

https://brainmass.com/physics/acceleration/physics-magnitude-force-acceleration-274195

#### Solution Summary

This posting contains answers to the given questions.

Physics: velocity, speed, force, temperature, energy, magnitude, acceleration, wave

1) A particle moves according to the equation x=10t2, where x is in meters and t is in seconds. Find the average velocity for the time interval from 2.0 second to 2.1 second.

A) 41 m/s

B) 100 m/s

2) If A = (12i -16j) and B = (-24i + 10j), what is the magnitude of the vector C = (2A - B)?

A) 42

B) 22

C) 64

D) 90

3) A room measures 3.0 m by 4.5 m by 6.0 m. The heating and air conditioning ducts to and from the room are circular with diameter 0.30 m, and the air in the room is to be exchanged every 12 minutes. What is the necessary flow speed in the duct? (Assume that the density of the air is constant)

A) 0.6 m/s

B) 1.6 m/s

C) 3.2 m/s

D) 4.1 m/s

5) A 50-kg ice skater is moving at 5 m/s when she grabs the loose end of a rope, the opposite end of which is tied to a pole. She then moves in a circle of radius 1 m around the pole. Determine the force exerted by the rope on her arms.

A) 1250 N

B) 250 N

C) 50 N

D) 1100 N

6) Steam at 1000C is added to ice at O0C. The mass of the steam is 10.0 g and the mass of the ice is 50.0 g. What is the final temperature of the mixture?

A) 20.4oC

B) 40.4oC

C) 80.8oC

D) 90.1oC

7) The speed of a 4.0-kg object is given by v = (2t) m/s, where t is in seconds. At what rate is the resultant force on this object doing work at t = 1 second?

A) 48 W

B) 40 W

C) 56 W

D) 16 W

8) A 10-kg object is initially at the top of a rise, at point A. It then moves down to point B. Choose point B to be the zero level for gravitational potential energy. Find the change in potential energy of the object if point B is 10 m lower than point A.

A) - 980

B) - 10

C) - 100

D) - 98

9) A 3-kg particle has a velocity of (3i - 4j) m/s. Find the magnitude of its momentum.

A) 9 kg.m/s

B) -12 kg.m/s

C) 15 kg.m/s

D) 3 kg.m/s

10) At t = 0, a wheel rotating about a fixed axis at a constant angular acceleration has an angular velocity of 2 rad/s. Two seconds later it has turned 5 complete revolutions. What is the angular acceleration of this wheel?

A) 17 rad/s^2

B) 14 rad/s^2

C) 20 rad/s^2

D) 23 rad/s^2

11) A car of mass 1000 kg moves with a speed of 50 m/s on a circular track of radius 100 m. What is the magnitude of its angular momentum (in kg.m^2/s) relative to the center of the racetrack?

A) 5 x 10^2

B) 5 x 10^6

C) 2.5 x 10^6

D) 2.5 x 10^4

14) How many significant figures are in the following number? 0.0064

A) 2

B) 3

C) 4

D) 5

15) In order to understand the concept of temperature it is useful to understand

A) the zeroth law of thermodynamics

B) the first law of thermodynamics

C) the second law of thermodynamics

D) none of the above

16) An archer shoots an arrow with a velocity of 45 m/s at an angle of 50 degrees with the horizontal. What is the height of the arrow at a point 150 meters downrange?

A) 4.7 m

B) 47.0 m

C) 5.6 m

D) 56.0 m

17) A sinusoidal wave is described by y=(0.30 m)sin(0.20x-40t ). Determine the wave speed.

A) 100 m/s

B) 133 m/s

C) 150 m/s

D) 200 m/s

18) The exhaust temperature of a Carnot heat engine is 350oC. What is the intake temperature if the efficiency is 25.0%?

A) 400oC

B) 543oC.

C) 558oC

D) 830oC

20) A house has well-insulated walls. It contains a volume of 100 m3 of air at 300 K. Calculate the energy required to increase the temperature of this diatomic gas by 2oC. Assume it is heating at constant pressure and use Cp=7R/2.

A) 118 kJ

B) 236 kJ

C) 354 kJ

D) 472 K

21) If the speed at some point in a fluid changes with time, the fluid flow is not __________.

A) steady

B) irrotational

C) incompressible

D) nonviscous

22) A bowling ball rolls without slipping on a flat surface. The ball has ___________.

A) rotational kinetic energy

B) translational kinetic energy

C) both a and b

D) neither a or b

23) In uniform circular motion, there is a ____________.

A) constant velocity

B) constant angular velocity

C) zero acceleration

D) net tangential acceleration

24) Linear momentum is ____________.

A) always conserved

B) a scalar quantity

C) a vector quantity

D) unrelated to force

25) If the net force on an object is zero, the object must _______________.

A) be at rest

B) be in motion with constant velocity

C) have zero acceleration

D) none of these