PHY-102: Energy and Circular Motion Exercises
review
Complete the following exercises.
A rifle with a longer barrel can fire bullets with a larger
... [Show More] velocity than a rifle with a shorter
barrel.
a. Explain this using the impulse-momentum theorem.
A rifle with longer barrel shoot shots with bigger speed when distinguished with rifle with shorter barrel, on the grounds that, as indicated by drive energy hypothesis, motivation is reliant on the connected power and time for which the power is connected (Impulse=Applied Force*Time). Longer barrel permits the extending gasses from black powder to push the projectile for the more drawn out time, which results in expanded speed or motivation.
b. Explain this using the work-energy theorem
Same marvels can likewise be clarified utilizing the work energy hypothesis, which expresses that work is equivalent to the change in motor vitality. As work is the capacity power and separation (Work=Force.Distance), while the dynamic vitality is the capacity of mass and speed (1/2 mv^2). In rifle, the growing gases apply a power on slug over some separation, which is the proportion of work done on the projectile. More the work is done, more will be K.E and eventually more will be the speed of shot. So if there should be an occurrence of long barrel rifles, the separation on which power is applied on the projectile increments and results in the expanded K.E when contrasted with the short barrel weapons.
So's the reason the shot discharged from the more drawn out barrels rifle will have more speed/speed than the one with short barrel.
2. Use physics terms to explain the benefits of crumple zones in modern cars.
Crumple zones are uniquely planned auxiliary regions situated at the front or back of autos to lessen the wounds because of accident. As indicated by the primary law of Newton, of a body is moving with certain speed, it will continue moving until some outside power stops it. For example, if a quick moving vehicle slams into divider, the vehicle will stop in the wake of impacting, yet the travelers inside the vehicle will continue pushing ahead with the speed of vehicle before impacting and will cause genuine wounds. Crumple zones are intended to diminish the effect of accident on the travelers by expanding the accident time and appropriating the accident power. As indicated by second law of Newton, the power relies upon the increasing speed and mass, and more the time the vehicle will take to come into rest, less the effect power experienced by the travelers. Crumple zones are normally made of delicate materials and on accident, they builds the season of accident by circulating its impact.
3. When a gun is fired at the shooting range, the gun recoils (moves backward). Explain this using the law of conservation of momentum.
Law of protection of energy expresses that, all out force of the shut framework stays consistent. If when slug is shot from the weapon, the firearm moves in reverse and this impact is known as the backlash.
This retrogressive development is because of the law of preservation of force, as both the firearm and projectile were very still before terminating, thus the complete energy is zero. At the point when slug is discharged from the weapon, it pushes ahead with the high speed, so as per law of protection energy, for this situation the firearm should go in reverse with a similar force to result into zero force.
Scientifically, let m1 is the mass of projectile, v1 is speed of slug in the wake of discharging, m2 is the mass of firearm and v2 is the speed of weapon in the wake of shooting. Along these lines, as indicated by the law of preservation of force.
What's more,
The negative sign in the articulation shows that both the weapon and shot will move inverse way after the gunfire to safeguard the general force of the framework.
4. Rank the following in terms of increasing inertia:
A. A 10,000 kg train car at rest
B. A 100 kg person running at 5 m/s
C. A 1200 kg car going 15 m/s
D. A 15 kg meteor going at a speed of 1000 m/s
4. D, B, C, A
5. Rank the following in terms of increasing momentum:
A. A 10,000 kg train car at rest
B. A 100 kg person running at 5 m/s
C. A 1200 kg car going 15 m/s
D. A 15 kg meteor going at a speed of 1000 m/s
5. A, B, D, C
6. Rank the following in terms of increasing kinetic energy:
A. A 1200 kg car going 15 m/s
B. A 10,000 kg train car at rest
C. A 15 kg meteor going at a speed of 1000 m/s
D. A 100 kg person running at 5 m/s
6. B, D, A, C
7. Ben (55 kg) is standing on very slippery ice when Junior (25 kg) bumps into him. Junior was moving at a speed of 8 m/s before the collision and Ben and Junior embrace after the collision.
The combine speed of the Ben and Junior after the collision = Vf = 2.5 m/s Mass of the Ben = Mb = 55 Kg
Mass of the Junior = Mj = 25Kg
The speed of the Junior before the collision = Vij= 8m/s The speed of the Ben before the collision = Vib = 0m/s
The combine speed of the Ben and Junior after the collision = Vf = ?
From the law of conservation of linear momentum , " The total momentum of an isolated system remains constant" . The isolated system is a system in which neither mass can enter or leave the system nor Energy can enter or leave the system.
SO,
Total momentum before the collision = Pi= Mb Vib + Mj Vij Total momentum after the collision = Pf = Vf ( Mb + Mj)
As, from the Law of conservation of momentum , the total momentum before the collision is equal to the total momentum after the collision
Total momentum before the collision = Total momentum after the collision
Pi = Pf
Mb Vib + Mj Vij = Vf ( Mb + Mj)
Arranging for Vf
Vf =( Mb Vib + Mj Vij) / ( Mb + Mj)
Vf =[ (55Kg)(0m/s) + (25Kg)(8m/s) ] / ( 55Kg + 25Kg)
Vf = (200 Kg m/s ) / (80Kg) Vf = 2.5 m/s
The speed of the Ben and Junior after the collision as they move across the ice is 2.5 m/s
8. Identical marbles are released from the same height on each of the following four frictionless ramps.
Compare the speed of the marbles at the end of each ramp. Explain your reasoning.
9. A force of only 150 N can lift a 600 N sack of flour to a height of 0.50 m when using a lever as shown in the diagram below.
a. Find the work done on the sack of flour (in J). Work done on the sack of flour is to be determined, for which the data given is as per the following.
600(0.5) =300
b. Find the distance you must push with the 150 N force on the left side (in m). Thus, the work done on the sack of flour will be
150(d)=300 d=300 equals 2m 150
c. Briefly explain the benefit of using a lever to lift a heavy object.
A lever is one of the six straightforward machines that upgrade the information power to give huge yield power that can lift substantial loads. This impact is likewise called leverage. In basic words, by utilizing lever, with little exertion enormous burdens can be lifted. Expected exertion to lift the heap relies on the overall separation of burden from the support of lever.
10. Rank the following in terms of increasing power.
A. Doing 100 J of work in 10 seconds.
B. Doing 100 J of work in 5 seconds.
C. Doing 200 J of work in 5 seconds.
D. Doing 400 J of work in 30 seconds. A, D, B, C [Show Less]