Angelica Therese B. Pacapac
T 12:00A-3:00P
I.
Physics for Engineers 1
March 26, 2022
Multiple Choice
1. The final momentum of a moving soccer ball is increased if the
a. force acting on it is increased c. velocity is increased
b. time of contact is increased
d. impulse is decreased
2. Which has a greater momentum, a large car moving at 30.0 m/s or a small car moving
at 30.0 m/s?
a. the large car
c. both cars
b. the small car
d. none of the above
3. A hammer is fallin at the rate of 3.00 m/s from the top of a tower accidentally hits the
head of a man who is passing by. How could the impact force experienced by the man
reduced?
a. Decrease the man’s velocity
c. decrease the impact time
b. Decrease the man’s mass
d. increase the impact time
4. A boy, whose mass is 50.0 kg is running very fast at the rate of 5.00 m/s when he
jumps onto a stationary cart with a mass of 3.00 kg. Assuming that the boy and the
cart move together, what is their common velocity?
a. 3.75 m/s b. 4.72 m/s c. 5.90 m/s
d. 7.35 m/s
5. A tennis ball is dropped from a height of 3.50 onto the floor. If the coefficient of
restitution between floor and ball is 0.85, how high will the ball bounce?
a. 1. 46 m b. 2.00 m
c. 2.53 m
d. 3.25 m
6. Which of the following statements is true for momentum?
a. Momentum is a scalar quantity
b. The standard unit on momentum in the MKS is the Joule
c. An object with mass only will have momentum
d. An object with a velocity has momentum
7. Which of the following statements is true about impulse?
a. Impulse is an example of a force
b. In a collision, the net impulse experienced by an object is equal to its
momentum change.
c. Stationary objects experience impulse.
d. The standard unit for impulse is the N ∙ m
8. All of the following statements about collisions are true EXCEPT?
a. Two colliding bodies, will exert equal forces upon each other even if
their masses are different
b. In collision, a body always experiences an impulse and a change in
momentum
c. In collision, the impulse which a body experiences is the same as its
velocity
d. In collision, two colliding bodies could have varied acceleration values
9. Which of the following statements is true about momentum?
a. Most collisions tend to be partially elastic then become completely elastic
b. Momentum is only conserved in elastic collision but not in inelastic
collision
c. The kinetis energy of an object remains constant during an elastic
collision
d. Elastic collisions occur when the collision force is a non-contact force
10. Which of the following has the greatest amount of momentum in relation to the
earth?
a. a mountain climber trailing Mt. Apo
b. a delivery truck speeding along a highway
c. a car truck parked in a parking lot
d. the Social Science building on the university campus
II.
PROBLEM – SOLVING
1. Initially an automobile is heading towards north at the rate of 27.6 m/s. Finally, the
speed was reduced to 4.20 m/s in the same direction. The automobile’s change in
momentum is 10 500 kg-m/s. Find the mass of the automobile.
Given:
Required:
Δp = 10 500 kg m/s
m
Vi = 27. 6 m/s
Vf = 4.20 m/s
Solution:
∆𝑝 = 𝑚(∆𝑣) = 𝑚 (𝑉𝑖 − 𝑉𝑓 )
10 500 𝑘𝑔 𝑚/𝑠 = 𝑚(27.6 𝑚/𝑠 − 4.20 𝑚/𝑠)
10 500 𝑘𝑔 𝑚/𝑠 = 𝑚(−23.4 𝑚/𝑠)
10 500 𝑘𝑔∙ 𝑚/𝑠
−23.4 𝑚/𝑠
=
𝑚 (−23.4 𝑚/𝑠)
−23.4 𝑚/𝑠
m = 448. 718 kg
2. A sled, with a mass of 1.40 x 102 kg, travels at a constant force in 4.75 s. The velocity of
the sled is initially zero and the final velocity is 7.97 m/s2, what is the change in
momentum? (b) What net force is exerted on the sled?
Given:
Required:
2
m = 1.40 x 10 kg = 140 kg
a. ∆𝑝
Vi = 0 m/s
b. FN
Vf = 7.95 m/s
∆𝑡 = 4.75 s
Solution:
a.
∆𝑝 = 𝑚(∆𝑣) = 𝑚 (𝑉𝑖 − 𝑉𝑓 )
∆𝑝 = 140 𝑘𝑔 ( 7. 95
𝑚
𝑚
−0 )
𝑠
𝑠
∆𝒑 = 𝟏𝟏𝟏𝟑 𝒌𝒈 ∙ 𝒎/𝒔
b.
𝐹𝑁 =
𝐹𝑁 =
∆𝑝
∆𝑡
1113 𝑘𝑔 ∙𝑚/𝑠
∆4.75 𝑠
𝑭𝑵 = 𝟐𝟑𝟒. 𝟑𝟏𝟔 𝑵
3. To improve the safety of motorist, modern cars are built so the front end crumples
upon impact. A 1200-kg car is travelling at a constant velocity of 8.0 m/s. It hits an
immovable wall and comes to a complete stop in 0.25 s.
(b) Calculate the impulse provided to the car
(c) What is the average net force exerted on the car?
(d) For the same impulse, what would be the average net force exerted
on the car if it had a rigid bumper and frame that stopped the car 0.40
s?
Given:
Required:
m = 1200 kg
a. I
Vo = 8.0 m/s
b. FN @ t = 0.25 s
∆𝑡 = 0.25 𝑠
c. FN @ t = 0.040 s
∆𝑡 = 0.25 𝑠
Solution:
a.
∆𝑝 = 𝑚(∆𝑣) = 𝑚 (𝑉𝑖 − 𝑉𝑓 )
𝑚
𝑚
− 8.0 )
𝑠
𝑠
𝑚
∆𝑝 = −9600 𝑘𝑔 ∙
𝑠
∆𝑝 = 140 𝑘𝑔 (0
∆𝑝 = 𝐼
𝑰 = −𝟗𝟔𝟎𝟎 𝑵 ∙ 𝒔
b.
𝐹𝑁 =
∆𝑝
∆𝑡
𝐹𝑁 =
−9600 𝑘𝑔 ∙𝑚/𝑠
0.25 𝑠
𝑭𝑵 = −𝟑. 𝟖𝟒 × 𝟏𝟎𝟒 𝑵
c.
𝐹𝑁 =
∆𝑝
∆𝑡
𝐹𝑁 =
−9600 𝑘𝑔 ∙𝑚/𝑠
0.40 𝑠
𝑭𝑵 = −𝟐. 𝟒 × 𝟏𝟎𝟓 𝑵
4. In a tennis game, a 0.2 kg ball moving at 15 m/s is hit by a racket. After the impact the
ball moves in the opposite direction with the velocity of 20 m/s. If the force F exerted
on the ball by the racket is 700 N, how long is the time contact?
Given:
Required:
m = 0.2 kg
Vi = 15 m/s
Vf = 20 m/s
F = 700 N
∆𝑡
Solution
∆𝑝 = 𝑚(∆𝑣) = 𝑚 (𝑉𝑖 − 𝑉𝑓 )
∆𝑝 = 0.2 𝑘𝑔 (20
𝑚
𝑚
− 15 )
𝑠
𝑠
∆𝑝 = 1 𝑘𝑔 ∙ 𝑚/𝑠
𝐼 = 1𝑁 ∙𝑠
𝐼 =𝐹∆𝑡
∆𝑡 =
∆𝑡 =
𝐼
𝐹
1𝑁 ∙𝑠
700 𝑁
∆𝒕 = 𝟎. 𝟎𝟎𝟏 𝒔