157

Physics Force & Laws Of Motion Level: High School

A rocket engine has the following thrust curve in pounds:

Time / Thrust: 0.13 second 99.061 pounds

Time / Thrust: 0.38 112.202

Time / Thrust: 0.63 118.164

Time / Thrust: 0.88 121.774

Time / Thrust: 1.14 123.731

Time / Thrust: 1.39 119.989

Time / Thrust: 1.64 115.161

Time / Thrust: 1.90 106.825

Time / Thrust: 2.15 94.019

Time / Thrust: 2.41 82.262

Time / Thrust: 2.66 48.434

Time / Thrust: 2.91 13.668

Time / Thrust: 3.17 3.033

Time / Thrust: 3.42 0.000

Burn timeâ€¦..: 3.420 seconds

Tavg Lbs (Average Thrust inPounds)â€¦..: 97.5776

Tavg Newtons. (Average thrust in Newtons): 434.047

Totlmp Lbsecs: (Total Impulse in PoundSeconds) 292.326

Totlmp Ntsecs:(Total Impulse in NewtonSeconds) 1300.330

The rocket engine is attached to the rear of a small bicycle. The weight of the bike and the motor is 35 lbs. The rider weighs 155 lbs. The bike has good bearings and tires, and rolls easily. The rider is bent down low to reduce the drag of air resistance. The track is straight and flat.

From a dead stop the rocket motor is ignited. What will be to top speed of the bike in mph(Miles per hour) and how far will it have traveled at motor burn out ? Will speed continue to increase at all beyond motor burn out ?

156

Physics Force & Laws Of Motion Level: High School

A bucket of water can be whirled in a vertical circle without the water spilling out , even at the top of the circle when the bucket is upside down . Explain .

155

Physics Force & Laws Of Motion Level: High School

Suppose a car moves at constant speed along a mountain road . At what places does it exert the greatest and least forces on the road :

(a) at the top of the hill

(b) at a dip between two hills

(c) On a level stretch near the bottom of a hill ?

154

Physics Force & Laws Of Motion Level: High School

It is sometime said that water is removed from clothes in a spin dryer by centrifugal force throwing the water outward . Is this correct ?

153

Physics Force & Laws Of Motion Level: High School

Find the tension in the rope and the force a 52.0 kg mountain climber must exert with her feet on the vertical rock face to remain stationary . Assume that the force is exerted parallel to her legs . Assume negligible force exerted by her arms .

152

Physics Force & Laws Of Motion Level: High School

A shopper pushes a grocery cart by exerting a force on the handle at a downward angle of 35.0 degrees below the horizontal . The loaded cart has a mass of 28.0 kg and the force of friction is 60.0 N

(a) What force must the shopper exert to move at a constant velocity ?

151

Physics Force & Laws Of Motion Level: High School

The other night my wife and I were about ready to push our airplane back into its hanger after an early evening flight . A fueler , who had just refilled our fuel tanks, was going to help guide us as we used a tow-bar to push the plane back . As we were reaching to the tow-bar the fueler asked how we could actually be able push the plane in. He cited Newtons third Law of Motion as the reason, explaining that when we push on the plane, the plane will pull back on us with an equal force , the force will cancel , and there will be no motion . Thus, we shouldn't be able to push the plane into place . What is wrong with the fuelers argument and what would you say that would be the correct evaluation of the situation .
When we push the plane , the force is being applied on the plane . When the reaction force due to plane acts on us , it is equal and opposite and it acts on a different body ie, us . Since the equal and opposite force are acting on different bodies , They can cause motion in the bodies . Only equal and opposite forces acting on the same body cancel .

150

Physics Force & Laws Of Motion Level: High School

A typical GPS satellite orbits at an altitude of 2.00x 10^7m . Find the orbital period , orbital speed , and the acceleration due to gravity at that altitude .

149

Physics Force & Laws Of Motion Level: High School

I was dragging a 45.0 kg box down the driveway and out to the curb for garbage pick-up on Tuesday evening . I was able to pull it on a horizontal surface at a constant velocity . I noticed that I exerted a force of magnitude of 145N directed at an angle of 20.0(DEG) above the horizontal . Determine the coefficient of kinetic friction between the box and the driveway .

148

Physics Force & Laws Of Motion Level: High School

If you weigh yourself at the equator you get a smaller value than if you weigh yourself at one of the poles . Explain why ? . (earth rotates so you are moving in a circular path at the equator )

147

Physics Force & Laws Of Motion Level: High School

Consider a .0750 kg airplane tied to the ceiling with a string . When the airplane's motor is started the plane moves in a horizontal circle radius . 400 m with a constant speed of 1.21m/s . Find the angle the string makes with the vertical and the tension in the string .

146

Physics Force & Laws Of Motion Level: High School

Imagine that there is a forward who sits in front of the goal crease . The goalie (mass = 77.5 kg ) pushes the forward (mass = 97.2 kg ) away . If the acceleration of the forward is 0.847m/s^2 , find the magnitude of the acceleration of goalie . Explain your reasoning .

61

Physics Force & Laws Of Motion Level: High School

Bock A with a mass of 10 kg , rests on a 30 degree incline , the coefficient of friction is 0.2 . The attached string is parallel to the incline and passes over a massless frictionless pulley at the top . Block B , with a mass of 3.0 kg , is attached to the dangling end of the string. Find the acceleration of the bock B .

60

Physics Force & Laws Of Motion Level: High School

A 120 lb person is being lifted aloft by a rocket which accelerates uniformly to an upward speed of 300 ft/sec. in 2 sec .

a. What is the upward acceleration in multiples of g?

b. What is apparent weight of the person during acceleration?

59

Physics Force & Laws Of Motion Level: High School

A 640 N acrobat falls 5.0 m from rest into a net. The net tosses him back up with the same speed he had just before he hit the net. Find the average force exerted on him by the net during this collision.

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