1211

Physics Force & Laws Of Motion Level: High School

While ice-skating you push off a wall with a force of 100 N . Calculate your acceleration if you have a mass of 50 kg and the coefficient of sliding friction between your skates at the ices is 0.09 .



1208

Physics Force & Laws Of Motion Level: High School

A particle of mass 3 kg rests on smooth horizontal table and attached to string 1.2 m long to fixed point in table . if particle moves in a horizontal circle with constant speed of 2.4 ms^-1 find the tension in the string ?



1204

Physics Force & Laws Of Motion Level: High School

A 3.0 kg mass is sliding on a horizontal frictionless surface with a speed of 3.0 m/sec when it collides with a 1.0 kg mass initially at rest as shown in the figure at “click here” . The masses stick together and slide up a frictionless circular track of radius 0.40 m . To what maximum height , h, above the horizontal surface will the masses slide ?



1201

Physics Force & Laws Of Motion Level: High School

Conservation of momentum

An astronaut outside a spaceship hammers a loose rivet back in place . What happens to the astronaut as he swing the hammer ?



1200

Physics Force & Laws Of Motion Level: High School

A pitcher claims he can throw a baseball with as much momentum as a 3.00 gram bullet moving with a speed of 1500 m/sec . A baseball has a mass of .145 kg . What must be its speed if the pitcher’s claim is valid ?



1199

Physics Force & Laws Of Motion Level: High School

Conservation of momentum

A u-238 nucleus (mass = 238 units) decays , transforming into an alpha particle (mass = 4 units) and a residual thorium nucleus (mass = 234 units) if the uranium nucleus was at rest , and the alpha particle has a speed of 1.5 x 10^7 m/sec , determine the recoil speed of the thorium nucleus . Include a sketch in your solution .



1198

Physics Force & Laws Of Motion Level: High School

A child bounces a 50 gram superball on the sidewalk . The velocity of the superball changes from 21 m/sec downward to 19 m/sec upward . If the contact time with the sidewalk is 1/800 sec , What is the magnitude of the force exerted on the superball by the sidewalk ?



1195

Physics Force & Laws Of Motion Level: High School

Atilla (mass M1 = 4.03 kg ) has fallen into a well . A freak earthquake has set the water in the well spinning (W1 = 4.03 Rad/sec) about a vertical axis thus carrying Atilla around and around . The radius of the well is R1 = 20.6 cm. Calculate atilla’s centripetal acceleration , Ac , the centripetal force on Atila, Fc, and Atilla’s tangential velocity , V1 .



1193

Physics Force & Laws Of Motion Level: High School

On the day of accident my partner and I repaired the chimney of a 20 meter call building .When we completed our work we noticed we had some bricks left over on the roof . To get them down we put them in a barrel, I then tied the rope to my truck . I swung the barrel out and loaded it with bricks. When we united the rope I was jerked off the ground suddenly lost my presence of mind , and forgot to let go of the rope . I proceeded up the side of the building at a rapid pace . At the third floor I meet the barrel which was now proceeding downward at an impressive rate, causing serious injury. Slowed only slightly by my collision with the barrel , I continued my rapid ascent , not stopping until my fingers of my right hand were two knuckles deep into the pulley. I was able to hold lightly onto the rope spite the excruciating pain I was experiencing , at this same time the barrel hit the ground and all the bricks fell out of the bottom. As you can imagine I began a very rapid descent down the building. Again at the 3rd floor I meet the barrel again , however this time the barrel slowed me down just enough to lessen my injuries when I fell onto the pile of bricks. As I layed on the pile of bricks I let go of the rope, only to see the barrel fall six storied right on top of me .

I have a mass of M1 = 72.1 kg

Barrel has mass of M2 = 22.9 kg

Bricks have mass M3 = 99.9 kg.

The pulley has mass M4 = 14.4 kg

The pulley has radius R = .31 meter.

Calculate how long it took this accident to run its course. Assume that all collisions with the barrel occur at 10.0 meters . Assume further that all collisions stop the motion for an instant and that all subsequent motion begin with zero initial velocity



1187

Physics Force & Laws Of Motion Level: High School

An object is held in place by friction on an inclined surface . The angle of inclination is increased until the object starts moving . If the surface is kept at this angle , the object ,

a. slows down.

b. moves at uniform speed

c. speeds up.

d. none of the above.




1186

Physics Force & Laws Of Motion Level: High School

A constant force is exerted on a cart that is initially at rest on an air track . Friction between the cart and the track is negligible . The force acts for a short time interval and gives the cart a certain final speed . To reach the same final speed with a force that is only half as big , the force must be exerted on the cart for a time interval l

a. four times as long as

b. twice as long as

c. equal to

d. half as long.

e. a quarter of




1185

Physics Force & Laws Of Motion Level: High School

A block of mass M is at rest on an inclined plane and is connected to an object of the same mass as shown in the diagram . Both the rope and the pulley have negligible masses , and the pulley has excellent ball bearings , so it is nearly frictionless . The coefficient of friction between the bock and the plane is M(sub s). What is the magnitude of the static frictional force in terms of M, g and angle theta



1184

Physics Force & Laws Of Motion Level: High School

A 300 g ball is hit by a bat and leaves the bat at 100 Km/hr . Find the force on the bat if the collision lasts for 2 milliseconds .



1183

Physics Force & Laws Of Motion Level: High School

A 300 g ball is hit by a bat and leaves the bat at 100 Km/hr . Find the force on the bat if the collision lasts for 2 milliseconds .



1182

Physics Force & Laws Of Motion Level: High School

Conservation of linear momentum

A 10 gram arrow is fired at 600 m/s into a 10 kg wooden block at rest, and gets embedded in it . Find the speed of the block .

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