When the momentum of a punch is stopped by the fighter's jaw, he rides with the punch so as to
1) decrease the velocity of the blow,
2) increase the time of contact of the blow,
and thereby reduce the
3) force.
4) impulse.
5) momentum.
6) energy.
[Ques. 2] According to the equation Ft = change in (mv), a foam rubber dashboard is safer than a metal one, for the force of impact, F, of an occupant against the dash is lessened in an accident. In this case, the m in this equation represents the
1) mass of the car,
2) mass of the person,
3) momentum of the car,
4) momentum of the person,
and the v represents the
5) velocity of the car.
6) speed at which the person hits the dashboard.
7) relative velocity between cars in a collision.
8) change in velocity, which is 10 m/s2.
[Ques. 3] As the ball rolls from the straight path from A to B its velocity increases and its acceleration
1) increases,
2) decreases,
3) remains constant,
and as it rolls from B to C its acceleration along the path
4) increases.
5) decreases.
6) remains constant.
[Ques. 4] As the ball rolls from A to B its velocity increases and its acceleration
1) increases;
2) decreases;
3) remains constant;
and when it rolls from B to C its acceleration along the path
4) increases.
5) decreases.
6) remains constant.
[Ques. 5] A horizontal 100-N force exerted against a 1000-N block causes the block to slide on a level surface with constant velocity. The friction force on the block must be
1) zero.
2) 100 N.
3) 1000 N.
4) greater than 1000 N.
In this case the pushing force and the friction force are
5) equal but oppositely directed.
6) an action-reaction pair.
7) both of these.
8) none of these.
[Ques. 6] A skydiver jumps through the air from a high-flying plane. As her velocity of fall increases, the net force acting on her
1) increases also,
2) decreases,
3) remains unchanged,
and her acceleration
4) increases.
5) decreases.
6) remains unchanged.
[Ques. 7] A stone is thrown downward from a tall cliff and hits the ground below. If it were instead thrown straight upward with the same initial speed, it would end up striking the ground below (neglect air resistance) with
1) the same speed.
2) less speed.
3) greater speed.
If air resistance IS a factor, then when the stone is moving downward it will undergo
4) an increase in acceleration as velocity increases.
5) a decrease in acceleration as velocity increases.
6) a constant acceleration.
[Ques. 8] If a constant net force is applied to a body, the body is
1) accelerating.
2) moving at constant speed.
3) at rest or moving at constant velocity.
If a body is moving at constant velocity, it must have
4) a constant net force acting upon it.
5) constant non-zero acceleration.
6) constant speed.
7) none of the above.
[Ques. 9] The net force that acts on a 100-N freely falling body is
1) zero,
2) 9.8 N,
3) 100 N,
and its acceleration is
4) zero.
5) 9.8 m/s2.
6) 100 m/s2.
[Ques. 10] A 200-N weight hangs motionless from a string that is attached to the ceiling. The net force acting on the weight is
1) zero,
2) 100 N,
3) 200 N,
and if the string breaks, the net force acting on the weight will be
4) zero.
5) 100 N.
6) 200 N.
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