Physics 101 mechanics help -- Bullet fired by a rifle barrel

AI Thread Summary
The discussion focuses on calculating the acceleration and position of a bullet fired from a rifle, with the speed equation given as v = (−5.00 ✕ 10^7)t² + (2.80 ✕ 10^5)t. The acceleration is derived as a = dv/dt, resulting in a = 2(5*10^5)t + 2.8*10^5, indicating the bullet's acceleration is 2.8*10^5 m/s² at t=0. There is confusion regarding the sign change in the derivative, prompting a request for clarification on the calculations. The thread emphasizes the importance of checking derivatives and completing all parts of the problem for accurate results.
EishaR
Messages
1
Reaction score
0
Homework Statement
A repeating rifle fires 2 LR bullets such that as they travel down the barrel of the rifle their speed is given by v = (−5.00 ✕ 107)t2 + (2.80 ✕ 105)t,where v is in meters per second and t is in seconds. The acceleration of the bullet just as it leaves the barrel is zero.
Determine the acceleration (in m/s2) and position (in m) of the bullet as a function of time when the bullet is in the barrel. (Use the following as necessary: t. Round all numerical coefficients to at least three significant figures. Do not include units in your answers. Assume that the position of the bullet at t = 0 is zero.)
a (t)=
x(t)=

(b)Determine the length of time the bullet is accelerated (in s).

(c) Find the speed at which the bullet leaves the barrel (in m/s).

(d) What is the length of the barrel (in m)?
Relevant Equations
y v = (−5.00 ✕ 10^7)t2 + (2.80 ✕ 10^5)t,
a) a= dv/dt = 2(5*10^5)t+2.8*10^5
2(5*10^5)(0)+2.8*10^5=2.8*10^5m/s^2
 
Physics news on Phys.org
EishaR said:
Homework Statement:: A repeating rifle fires 2 LR bullets such that as they travel down the barrel of the rifle their speed is given by v = (−5.00 ✕ 107)t2 + (2.80 ✕ 105)t,where v is in meters per second and t is in seconds. The acceleration of the bullet just as it leaves the barrel is zero.
Determine the acceleration (in m/s2) and position (in m) of the bullet as a function of time when the bullet is in the barrel. (Use the following as necessary: t. Round all numerical coefficients to at least three significant figures. Do not include units in your answers. Assume that the position of the bullet at t = 0 is zero.)
a (t)=
x(t)=

(b)Determine the length of time the bullet is accelerated (in s).

(c) Find the speed at which the bullet leaves the barrel (in m/s).

(d) What is the length of the barrel (in m)?
Relevant Equations:: y v = (−5.00 ✕ 10^7)t2 + (2.80 ✕ 10^5)t,

a) a= dv/dt = 2(5*10^5)t+2.8*10^5
2(5*10^5)(0)+2.8*10^5=2.8*10^5m/s^2
For the first part, check your derivative. You must attempt the other parts also.
 
Last edited:
How did −5.00 ✕ 10^7 turn into +5.00 ✕ 10^5?
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »
Thread 'Minimum mass of a block'

Thread 'Minimum mass of a block'

Here we know that if block B is going to move up or just be at the verge of moving up ##Mg \sin \theta ## will act downwards and maximum static friction will act downwards ## \mu Mg \cos \theta ## Now what im confused by is how will we know " how quickly" block B reaches its maximum static friction value without any numbers, the suggested solution says that when block A is at its maximum extension, then block B will start to move up but with a certain set of values couldn't block A reach...
View full post »

Similar threads

Kinematics: two runners with different and non-constant accelerations
Replies
2
Views
978
Physics rifle problem -- Forces and acceleration of the bullet
Replies
1
Views
2K
Help with question on motion: Avoiding a rear-end collision
Replies
6
Views
3K
Newton's laws of motion: A gun firing bullets....
Replies
16
Views
3K
Calculating Average Net Force Exerted on a 15-g Bullet Fired from a Rifle
Replies
14
Views
3K
Block pulled up the incline problem
Replies
22
Views
3K
Correct Derivation of the Adiabatic Condition? (PV Diagram)
Replies
4
Views
1K
Solving Kinematics and Conservation of Energy Problems | Physics Homework
Replies
9
Views
3K
Homework help with interpreting SUTAV questions
Replies
5
Views
1K
Find the average force exerted on a bullet by a rifle
Replies
1
Views
3K

Hot Threads

Recent Insights

Back
Top