True/false 1. In open system the sum of total linear momentum is constant.
2. In a system of change of momentum in a collision while the time of contact is longer, its impact of force decrease.
3. In an elastic collision, the kinetic energy is not conserved.
4. A system of an object is in linear equilibrium, if there is a resultant force act on it.
5. When a ball is bounce back on the ground, its momentum is conserved and its height is decreasing.
II. Choose
6. A car has a mass of 1400kg, travelling with a velocity 15m/s and collides with street light pole. Calculate its impulse while it stops A. 20,000Ns
B. -21,000Ns
C. 14,000Ns
D. Zero
7. A boxer moves his head backward when his opponent blows a punch, why?
A. To increase the force of the impact
B. To increase its momentum
C. To decrease the impact of force by increasing time interval.
D. To stop the change of momentum
8. A pink ponk player hit a ball of 400g, with a force of 70N, by a racket. The time of contact between a racket and a ball is 0.02s. calculate its change of momentum A. 1.4kg m/s
B. 8kg m/s
C. 28kg m/s
D. 2kg m/s
9. A 3kg rifle fires a 30g bullet horizontally. If the rifle recill velocity is 2m/s. calculate the velocity of the bullet.
A. 0.001m/s
B.60m/s
C. 6m/s
D.200m/s
10.A car of mass 1400kg is moving with a velocity of 24m/s to the right. It collides with a truck of mass 18,000kg, moves at a speed of 12m/s to the left and stick together. Calculate the combined velocity.
A. 1.7m/s
B. 11.1 m/s
C. 9.4 m/s
D. 12.8 m/s
11.A target of mass 400g moving with a horizontal velocity of 10m/s is hit by a bullet of mass 0.02kg moving in the opposite direction. If both the bullet and the target come to rest after the collision calculate the velocity of the bullet at the time of striking the target.
A. 200m/s
B. 100m/s
C. 50m/s
D. 2000m/s
12.A squash player hit a squash ball and it move with a velocity 8m/s. it bounce back at 6m/s. if the mass of a ball in 500g, calculate the change of momentum
A. -1 kg m/s
B. -7kg m/s
C.-5kg m/s
D. zero
13.A monkey carries a banana and slides down to wards a cliff, but when it throws a banana forward, it stops at the edge, and safe from danger, why?
A. Because of friction force
B. Because of un balanced force C. Because of inertia
D. Because for every action there equal and opposite reaction force.
14.A body of mass 30kg in pushed on a horizontal surface by a force of 500N in the horizontal direction. The coefficient of kinetic friction in 0.2. calculate the acceleration of the body and the distance moved, if the body start from rest and takes 10sec.
A. 14.7m/s2, 735m
B. 18.3m/s2, 915m
C. 16.6 m/s2, 830m
D. 6.7m/s2, 330m
15.A block slide down on an inclined plane at angle of 370 to the horizontal. The coefficient of kinetic friction is 0.3. calculate the acceleration of the block. Use g= 10m/s2
A. 6m/s2
B. 8m/s2
C. 3.6m/s2
D. 2.4m/s2​