Question

Please can someone double-check my answers?

1) A ball with a mass of 0.15 kg has a velocity of 5m/s. It strikes a wall perpendicularly and bounces off straight back with a velocity of 3 m/s. The ball underwent a change in momentum of?

1.20 kg*m/s

2) What braking force is supplied to a 3,000 kg car traveling with a velocity of 35 m/s that is stopped in 12 seconds?

F=8750 N

3) A 0.1 kg baseball is thrown with a velocity of 35 m/s. The batter hits it straight back with a velocity of 60 m/s. What is the magnitude of the average impulse exerted on the ball by the bat?

9.5 N*s

4) A 1 kg object is moving with a velocity of 6 m/s to the right. It collides and sticks to a 2 kg object moving with velocity of 3 m/s in the same direction. How much Kinetic energy is lost in the collision?

3J

5) A 2 kg mass moving with a velocity of 7 m/s collides elastically with a 4 kg mass moving in the opposite direction at 4 m/s. The 2 kg mass reverses direction after the collision and has new velocity of 3 m/s. What is the velocity of the 4 kg mass?

1 m/s

6) A mass of 3 kg is attached to a massless spring with a force constant 500 N/m. The mass rests on a horizontal frictionless surface. The system is compressed a distance of 30 cm from the springs initial position and then released. The momentum of the mass when the spring passes its equilibrium position is?

8660.25m/s

7) Can an object have energy without having momentum? Explain.

Yes an object can have energy without having momentum. For example, a rock that is at the top of a cliff has potential energy since it's not moving but there is no momentum.

8) Can an object have momentum without having energy? Explain.

No object that has momentum also has energy. This is because if the velocity is not then the kinetic energy is also not 0 momentum is a vector, but energy is a scalar.

9) An object of mass 2 kg has a linear momentum of 6 kg. m /s. What is this objects Kinetic energy?

9J

10) A box with a mass of 2 kg accelerates in a straight line from 4 m/s to 8 m/s due to the application of a force whose duration is 0.5 seconds. Find the average strength of this force?

16N

11) A 45 kg. girl is sitting on a seesaw 0.6 m from the balance point. How far, on the other side, should a 60 kg. boy sit so that the seesaw will remain in balance?

0.45m

12) A solid cylinder consisting of an outer radius R1 and an inner radius R2 is pivoted on a frictionless axle as shown. A string is wound around the outer radius and is pulled to the right with a force F1 = 3N. A second string is wound around the inner radius and is pulled down with a force F2 = 5N. If R1 = 0.75 m and R2 = 0.35m, what is the net torque acting on the cylinder?

-0.5Nm

15) An object of mass 0.5 kg., moving in a circular path of radius 0.25 m, experiences a centripetal acceleration of constant magnitude 9 m/s2 . What is the objects angular speed?

6 rad/sec

16) An object, originally at rest begins spinning under uniform angular acceleration. In 10 seconds, it completes an angular displacement of 60 rad. What is the value of its angular acceleration?

1.2 rad/s^2

17) The moment of Inertia of a solid uniform sphere of mass m and radius R is given by the equation I = (2/5) mR2 . Such a sphere is released from rest at the top of an inclined plane of height h= 10 m, length L, and the incline angle Ω. If the sphere rolls without slipping, find the linear speed at the bottom of the incline.

11.83m/s

18) An object spins with angular velocity 10 rad/s. If the objects moment of Inertia increases by a factor of 2 without the application of an external torque, what will be the object’s new angular velocity?

1/2 angular velocity (w)

19) A 0.05 kg ball is thrown upward from the ground with an initial velocity of 30 m/s. At its maximum height, the magnitude of the balls acceleration is?

9.80 m/s^2

20) A 15 Newton force is applied to a mass M that is adjacent to a wall, as shown. If the mass is 2 kg, the force that the wall exerts on the mass is equal to?

15N

Answer 1

1. Initial Momentum,

Final momentum,

change in momentum is,

Negative sign depends on the direction you take to be positive or negative. hence change in momentum is 1.2 kgm/s

2. time taken,

initial speed,

final speed,

using the first equation of motion,

Braking force required is,

3. initial velocity, (direction of initial velocity is taken as positive direction)

final velocity,

change in impulse is,

4. Initial momentum of object 1 is,

Initial momentum of object 2 is,

Let the final speed after the collision of both objects be

Final momentum,

Conserving the momentum,

Initial kinetic energy is,

Final Kinetic Energy is,

Loss in Kinetic Energy is,